Merge branch 'fix/release-build-jni-keep-rules'

Release builds aborted on the first callback of every test: R8 renamed the
IperfCallback implementation and its methods, so the JNI GetMethodID lookups
resolved nothing. Adds the keep rules, and makes the native side report a
failed lookup instead of aborting the process on the next JNI call.

Debug builds do not minify, so every on-device check until now passed while the
shipping artifact was broken. Found by running the release APK during release
preparation.

Verified with the release APK on an XQ-AS72: clean run at 806 Mbits/sec,
matching the server's own figure.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

android/app/build.gradle.kts

@@ -37,6 +37,13 @@ android {
             // TODO: Add your own signing config for the release build.
             // Signing with the debug keys for now, so `flutter run --release` works.
             signingConfig = signingConfigs.getByName("debug")
+
+            // proguard-rules.pro keeps the names JNI resolves at runtime.
+            // Without it a release build aborts on the first callback.
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro",
+            )
         }
     }
 

android/app/proguard-rules.pro

@@ -0,0 +1,21 @@
+# JNI reaches these by name. R8 renames by default, so without these rules a
+# release build resolves nothing: GetMethodID("onOutput", ...) returns NULL,
+# raises NoSuchMethodError, and the next JNI call aborts the process with
+#   NoSuchMethodError: no non-static method "Lp0;.onOutput(Ljava/lang/String;)V"
+# Debug builds do not minify, so this only ever appears in release.
+
+# The plugin object holds the native method declarations and is looked up from
+# C by its fully qualified name (Java_com_novoyuuparosk_iperf3gui_IperfRunner_*).
+-keep class com.novoyuuparosk.iperf3gui.IperfRunner { *; }
+
+# The callback interface and everything implementing it: iperf_jni.c resolves
+# onOutput/onError/onComplete by name on the concrete object's class, so the
+# implementors' method names must survive too, not just the interface's.
+-keep interface com.novoyuuparosk.iperf3gui.IperfRunner$IperfCallback { *; }
+-keep class * implements com.novoyuuparosk.iperf3gui.IperfRunner$IperfCallback { *; }
+
+# Belt and braces for any future native method: keep the name of any class
+# declaring one, and the native methods themselves.
+-keepclasseswithmembernames,includedescriptorclasses class * {
+    native <methods>;
+}

android/app/src/main/cpp/iperf_jni.c

@@ -5,16 +5,25 @@
  * the Flutter app to run iperf3 tests natively inside the app process
  * (no Process.start needed, no SELinux restrictions).
  *
+ * OUTPUT NOTE:
+ * The test runs in --json-stream mode with a json_callback installed, so
+ * iperf3 hands each event ("start", "interval", "end", "error") straight to
+ * us as a JSON string and never touches test->outfile. That is what the hook
+ * exists for -- iperf.h calls it "allow user apps to receive the JSON
+ * strings, instead of writing them to the output file".
+ *
+ * An earlier version piped test->outfile to a reader thread instead. That
+ * required closing the pipe's write end before joining the reader (which
+ * blocks in fgets() until EOF) and single ownership of the shared state
+ * struct. Both were gotten wrong and deadlocked every test. Reading events
+ * from the callback removes the pipe, the reader thread, and that whole class
+ * of ordering bug.
+ *
  * THREADING NOTE:
  * runIperfLive() BLOCKS for the whole duration of the test. Kotlin must
  * call it from a worker thread, never from the Flutter platform thread.
- *
+ * json_callback fires on whichever thread iperf3 reports from, so it resolves
- * PIPE / SHUTDOWN NOTE:
+ * a JNIEnv for the calling thread rather than reusing a stored one.
- * iperf's output goes to a pipe drained by a reader thread that blocks in
- * fgets(). The reader only sees EOF once the write end is closed, so the
- * write end MUST be closed before pthread_join() — joining first deadlocks.
- * The state struct is owned solely by the JNI caller, which frees it after
- * joining the reader; the reader must never free it.
  *
  * SIGNAL HANDLING NOTE:
  * iperf3's run() function (called from iperf_run_client()) uses
@@ -61,21 +70,37 @@ static pthread_mutex_t g_test_mutex = PTHREAD_MUTEX_INITIALIZER;
 static volatile int g_stop = 0;
 static char g_tmp_template[1024] = "/data/local/tmp/iperf3.XXXXXX";
 
-/* Per-call state shared between the JNI caller and the reader thread.
+/* Per-call state, reachable from the json_callback.
- * We store the callback object (global ref) and method IDs.
  * Callbacks are invoked via CallVoidMethod, NOT as function pointers. */
 struct iperf_run_state {
     jobject callback_ref;       /* Global ref to the callback object */
     jmethodID mid_output;       /* Method ID for onOutput(String) */
     jmethodID mid_error;        /* Method ID for onError(String) */
     jmethodID mid_complete;     /* Method ID for onComplete() */
-    FILE *outfile;              /* Pipe write end; NULL once closed */
-    int pipe_fd[2];
     JavaVM *jvm;
-    pthread_t reader_thread;
-    int reader_started;         /* Only join if pthread_create succeeded */
 };
 
+/* iperf3's json_callback signature carries no user-data pointer, so the
+ * current run's state has to be reachable from a global. Only one test runs
+ * at a time (enforced in runIperfLive), and this is published before
+ * iperf_run_client() and cleared after it returns. */
+static struct iperf_run_state *g_current_state = NULL;
+
+/* Resolve a method ID, clearing the exception a failed lookup leaves behind.
+ *
+ * GetMethodID raises NoSuchMethodError on failure, and any further JNI call
+ * made while an exception is pending aborts the process. Returning NULL and
+ * clearing lets the caller fail on its own terms. */
+static jmethodID resolve_method(JNIEnv *env, jclass cls,
+                                const char *name, const char *sig) {
+    jmethodID mid = (*env)->GetMethodID(env, cls, name, sig);
+    if ((*env)->ExceptionCheck(env)) {
+        (*env)->ExceptionClear(env);
+        return NULL;
+    }
+    return mid;
+}
+
 /* Helper: invoke the output callback via CallVoidMethod */
 static void signal_output(JNIEnv *env, struct iperf_run_state *state,
                           const char *msg) {
@@ -108,50 +133,36 @@ static void signal_complete(JNIEnv *env, struct iperf_run_state *state) {
 }
 
 /* ------------------------------------------------------------------ */
-/* Output reader thread — reads from iperf's output pipe and forwards */
+/* json_callback — receives one JSON event string per report from      */
-/* each line to the Java callback via JNI.                            */
+/* iperf3 and forwards it to Java verbatim. Parsing happens in Dart.   */
 /*                                                                    */
-/* Exits when the write end of the pipe is closed (EOF). Does NOT own */
+/* Runs on iperf3's reporting thread. In the client that is the thread */
-/* `state`: the JNI caller frees it after joining this thread.        */
+/* that called iperf_run_client() (already attached, since Kotlin's    */
+/* executor thread is a Java thread), but GetEnv is checked rather     */
+/* than assumed, with an attach as fallback.                          */
 /* ------------------------------------------------------------------ */
-static void *reader_thread_func(void *arg) {
+static void json_event_callback(struct iperf_test *test, char *json) {
-    struct iperf_run_state *state = (struct iperf_run_state *) arg;
+    struct iperf_run_state *state = g_current_state;
-    JNIEnv *env;
+    if (!state || !json) return;
-    int ret;
 
-    /* Attach this native thread to the Java VM */
+    JNIEnv *env = NULL;
-    ret = (*state->jvm)->AttachCurrentThread(state->jvm, &env, NULL);
+    int attached = 0;
-    if (ret != JNI_OK) {
+
-        LOGE("AttachCurrentThread failed: %d", ret);
+    if ((*state->jvm)->GetEnv(state->jvm, (void **) &env, JNI_VERSION_1_6)
-        /* Still drain the pipe so writers never block on a full pipe. */
+            != JNI_OK) {
-        char drain[1024];
+        if ((*state->jvm)->AttachCurrentThread(state->jvm, &env, NULL)
-        while (read(state->pipe_fd[0], drain, sizeof(drain)) > 0) { }
+                != JNI_OK) {
-        close(state->pipe_fd[0]);
+            LOGE("json_event_callback: could not reach a JNIEnv");
-        return NULL;
+            return;
+        }
+        attached = 1;
     }
 
-    char buf[1024];
+    signal_output(env, state, json);
-    FILE *fp = fdopen(state->pipe_fd[0], "r");
-    if (fp) {
-        while (fgets(buf, sizeof(buf), fp) != NULL) {
-            /* Skip empty lines */
-            if (buf[0] == '\n' || buf[0] == '\0')
-                continue;
-            jstring line = (*env)->NewStringUTF(env, buf);
-            if (line != NULL) {
-                (*env)->CallVoidMethod(env, state->callback_ref,
-                                       state->mid_output, line);
-                (*env)->DeleteLocalRef(env, line);
-            }
-        }
-        fclose(fp); /* also closes pipe_fd[0] */
-    } else {
-        close(state->pipe_fd[0]);
-    }
 
-    /* Detach this native thread */
+    if (attached) {
         (*state->jvm)->DetachCurrentThread(state->jvm);
-    return NULL;
+    }
 }
 
 /* ------------------------------------------------------------------ */
@@ -198,30 +209,12 @@ static void free_argv(char **argv, int argc) {
     free(argv);
 }
 
-/* ------------------------------------------------------------------ */
-/* Close the pipe write end. Idempotent — both the normal and the      */
-/* longjmp path call it, and the second call must be a no-op.          */
-/*                                                                    */
-/* Closing this is what makes the reader thread see EOF and exit, so   */
-/* it must happen before any pthread_join().                           */
-/* ------------------------------------------------------------------ */
-static void close_outfile(struct iperf_run_state *state) {
-    if (state && state->outfile) {
-        fflush(state->outfile);
-        fclose(state->outfile);
-        state->outfile = NULL;
-    }
-}
-
 /* Retire the global test pointer and free it, under the mutex. */
 static void retire_test(void) {
     pthread_mutex_lock(&g_test_mutex);
     struct iperf_test *test = g_test;
     g_test = NULL;
     if (test) {
-        /* outfile is a closed FILE* by now — point it somewhere harmless so
-         * nothing in the teardown path can write to a dead stream. */
-        test->outfile = stdout;
         iperf_free_test(test);
     }
     pthread_mutex_unlock(&g_test_mutex);
@@ -236,14 +229,8 @@ static void iperf_cleanup_and_signal(JNIEnv *env,
                                      struct iperf_run_state *state,
                                      char **argv, int argc,
                                      int ret, int stopped) {
-    /* Close the write end FIRST: the reader thread is blocked in fgets()
+    /* No more events can be delivered once the run is over. */
-     * and only unblocks on EOF. Joining before this would deadlock. */
+    g_current_state = NULL;
-    close_outfile(state);
-
-    if (state->reader_started) {
-        pthread_join(state->reader_thread, NULL);
-        state->reader_started = 0;
-    }
 
     /* Restore default signal handlers before g_sigend_jmp_buf goes stale. */
     iperf_catch_sigend(SIG_DFL);
@@ -259,15 +246,11 @@ static void iperf_cleanup_and_signal(JNIEnv *env,
 
     /* Signal result to Java */
     if (user_stopped) {
-        signal_output(env, state, "[iPerf JNI] Test was stopped by user.\n");
+        signal_output(env, state, "{\"event\":\"jni_stopped\",\"data\":{}}");
     } else if (ret < 0) {
         char errbuf[256];
-        snprintf(errbuf, sizeof(errbuf),
+        snprintf(errbuf, sizeof(errbuf), "%s", iperf_strerror(i_errno));
-                 "[iPerf JNI] Test failed: %s\n",
-                 iperf_strerror(i_errno));
         signal_error(env, state, errbuf);
-    } else {
-        signal_output(env, state, "[iPerf JNI] Test completed successfully.\n");
     }
 
     /* Signal completion to Java */
@@ -304,13 +287,25 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
 
     /* Resolve callback method IDs up front so failures can be reported. */
     jclass callback_cls = (*env)->GetObjectClass(env, callback);
-    jmethodID mid_output = (*env)->GetMethodID(
+    jmethodID mid_output = resolve_method(
             env, callback_cls, "onOutput", "(Ljava/lang/String;)V");
-    jmethodID mid_error = (*env)->GetMethodID(
+    jmethodID mid_error = resolve_method(
             env, callback_cls, "onError", "(Ljava/lang/String;)V");
-    jmethodID mid_complete = (*env)->GetMethodID(
+    jmethodID mid_complete = resolve_method(
             env, callback_cls, "onComplete", "()V");
 
+    /* If the names did not resolve there is no way to report anything: the
+     * reporting path is the thing that is missing. Bail out loudly instead.
+     *
+     * In practice this means R8 renamed the callback in a release build and
+     * android/app/proguard-rules.pro has stopped covering it. */
+    if (!mid_output || !mid_error || !mid_complete) {
+        LOGE("Callback methods did not resolve (onOutput=%p onError=%p "
+             "onComplete=%p) — check the -keep rules for IperfCallback",
+             mid_output, mid_error, mid_complete);
+        return;
+    }
+
     /* Report a startup failure directly on the callback object and finish,
      * so Dart's completer always resolves instead of waiting for a timeout. */
     #define FAIL_EARLY(msg) do {                                              \
@@ -325,20 +320,20 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
         if (mid_complete) (*env)->CallVoidMethod(env, callback, mid_complete); \
     } while (0)
 
-    /* Refuse to start a second concurrent test — the globals below hold
+    /* Refuse to start a second concurrent test — the globals above hold
      * exactly one test's worth of state. */
     pthread_mutex_lock(&g_test_mutex);
     int busy = (g_test != NULL);
     pthread_mutex_unlock(&g_test_mutex);
     if (busy) {
-        FAIL_EARLY("[iPerf JNI] A test is already running.");
+        FAIL_EARLY("A test is already running.");
         return;
     }
 
     /* Create the iperf test object */
     struct iperf_test *test = iperf_new_test();
     if (!test) {
-        FAIL_EARLY("[iPerf JNI] Failed to create iperf test");
+        FAIL_EARLY("Failed to create iperf test");
         return;
     }
 
@@ -352,7 +347,7 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
     char **argv = build_argv(env, arguments, &total_argc);
     if (!argv) {
         retire_test();
-        FAIL_EARLY("[iPerf JNI] Failed to allocate argv");
+        FAIL_EARLY("Failed to allocate argv");
         return;
     }
 
@@ -365,19 +360,7 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
     if (iperf_parse_arguments(test, total_argc, argv) < 0) {
         char errbuf[256];
         snprintf(errbuf, sizeof(errbuf),
-                 "[iPerf JNI] Argument parse error: %s", iperf_strerror(i_errno));
+                 "Argument parse error: %s", iperf_strerror(i_errno));
-        free_argv(argv, total_argc);
-        retire_test();
-        FAIL_EARLY(errbuf);
-        return;
-    }
-
-    /* Create a pipe to capture iperf's output */
-    int pipefd[2];
-    if (pipe(pipefd) != 0) {
-        char errbuf[256];
-        snprintf(errbuf, sizeof(errbuf),
-                 "[iPerf JNI] Failed to create output pipe: %s", strerror(errno));
         free_argv(argv, total_argc);
         retire_test();
         FAIL_EARLY(errbuf);
@@ -389,25 +372,11 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
             calloc(1, sizeof(struct iperf_run_state));
     if (!state) {
         free_argv(argv, total_argc);
-        close(pipefd[0]);
-        close(pipefd[1]);
         retire_test();
-        FAIL_EARLY("[iPerf JNI] Failed to allocate run state");
+        FAIL_EARLY("Failed to allocate run state");
         return;
     }
 
-    FILE *outfile = fdopen(pipefd[1], "w");
-    if (!outfile) {
-        free(state);
-        free_argv(argv, total_argc);
-        close(pipefd[0]);
-        close(pipefd[1]);
-        retire_test();
-        FAIL_EARLY("[iPerf JNI] Failed to open output stream");
-        return;
-    }
-
-    /* Get JavaVM for reader-thread attachment */
     JavaVM *jvm;
     (*env)->GetJavaVM(env, &jvm);
 
@@ -415,14 +384,16 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
     state->mid_error = mid_error;
     state->mid_complete = mid_complete;
     state->callback_ref = (*env)->NewGlobalRef(env, callback);
-    state->outfile = outfile;
-    state->pipe_fd[0] = pipefd[0];
-    state->pipe_fd[1] = pipefd[1];
     state->jvm = jvm;
 
-    /* Redirect iperf's output to our pipe */
+    /* Deliver results as a stream of JSON events straight to
-    test->outfile = state->outfile;
+     * json_event_callback, rather than as text through test->outfile.
-    setvbuf(test->outfile, NULL, _IOLBF, 0); /* Line-buffered */
+     * --json-stream sets both of these flags, so setting json_stream alone
+     * would leave iperf3 printing human-readable text as well. */
+    iperf_set_test_json_output(test, 1);
+    iperf_set_test_json_stream(test, 1);
+    iperf_set_test_json_callback(test, json_event_callback);
+    g_current_state = state;
 
     /* Set temp directory for stream buffers (mkstemp in iperf_new_stream).
      * On Android, /data/local/tmp is NOT writable from the app sandbox —
@@ -430,22 +401,6 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
      * the strdup internally. */
     iperf_set_test_template(test, g_tmp_template);
 
-    /* Spawn reader thread to forward iperf output to Java. Started before
-     * the test so early output is not lost, and before setjmp so the
-     * longjmp path can rely on reader_started being accurate. */
-    if (pthread_create(&state->reader_thread, NULL,
-                       reader_thread_func, state) != 0) {
-        close_outfile(state);
-        close(pipefd[0]);
-        free_argv(argv, total_argc);
-        retire_test();
-        (*env)->DeleteGlobalRef(env, state->callback_ref);
-        free(state);
-        FAIL_EARLY("[iPerf JNI] Failed to start output reader thread");
-        return;
-    }
-    state->reader_started = 1;
-
     #undef FAIL_EARLY
 
     /*
@@ -462,8 +417,6 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
         signal(SIGPIPE, SIG_IGN);  /* Ignore SIGPIPE for socket errors */
         iperf_catch_sigend(sigend_handler);
 
-        signal_output(env, state, "[iPerf JNI] Starting iPerf3 client...\n");
-
         g_stop = 0;
         int ret = iperf_run_client(test);
         LOGI("iperf_run_client returned: %d i_errno=%d strerror=%s",
@@ -478,8 +431,8 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
     } else {
         /*
          * We got here via longjmp() from sigend_handler.
-         * iperf_cleanup_and_signal() closes the pipe, joins the reader and
+         * iperf_cleanup_and_signal() frees everything, so there is nothing
-         * frees everything, so there is nothing to unwind by hand here.
+         * to unwind by hand here.
          */
         LOGI("Test interrupted by signal %d", g_signed_sig);
         g_stop = 1;
@@ -515,19 +468,7 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_forceStopIperfTest(
     pthread_mutex_unlock(&g_test_mutex);
 
     if (!requested) return;
-
+    LOGI("Graceful stop requested");
-    /* Notify Java */
-    jclass callback_cls = (*env)->GetObjectClass(env, callback);
-    jmethodID mid_output = (*env)->GetMethodID(
-            env, callback_cls, "onOutput", "(Ljava/lang/String;)V");
-    if (mid_output) {
-        jstring msg = (*env)->NewStringUTF(env,
-                                           "[iPerf JNI] Requested graceful stop.\n");
-        if (msg) {
-            (*env)->CallVoidMethod(env, callback, mid_output, msg);
-            (*env)->DeleteLocalRef(env, msg);
-        }
-    }
 }
 
 /* ------------------------------------------------------------------ */

docs/README.md

@@ -6,19 +6,25 @@ A Flutter-based Android GUI wrapper for iperf3, the popular network performance
 
 ```
 lib/                          # Flutter/Dart application layer
-├── main.dart                 # App entry point (MaterialApp)
+├── main.dart                 # Composition root: picks the Iperf3Runner impl
-├── domain/                   # Business logic (platform-independent)
+├── main_headless.dart        # Runs a test with no widgets (see Layering)
+├── domain/                   # Pure Dart — no Flutter import
 │   ├── models/
 │   │   ├── test_configuration.dart   # Server, port, duration, interval, parallel streams
-│   │   └── iperf3_result.dart        # Raw output + exit code
+│   │   ├── iperf3_result.dart        # Raw output, exit code, stopped flag
-├── data/
+│   │   ├── iperf3_event.dart         # Parsed --json-stream reports
+│   │   └── iperf3_session.dart       # One run accumulated: samples, totals, stats
 │   └── services/
-│       └── iperf3_service.dart       # Dart → MethodChannel bridge (async with Completer)
+│       └── iperf3_runner.dart        # The contract the UI depends on
-└── ui/                       # Presentation layer
+├── data/                     # Transport — flutter/services only
+│   └── services/
+│       └── iperf3_service.dart       # Iperf3Runner over MethodChannel → JNI
+└── ui/                       # Presentation
     └── features/
         └── test_run/
-            ├── test_run_screen.dart          # Server/port inputs + GO button
+            ├── test_run_screen.dart            # Inputs, GO/STOP, live transcript
-            └── test_run_view_model.dart      # State machine: idle → running → completed/error
+            ├── test_run_view_model.dart        # idle → running → completed/error
+            └── iperf3_event_formatter.dart     # Events → iperf3-style text
 
 android/app/src/main/
 ├── kotlin/                     # Kotlin plugin layer
@@ -42,11 +48,55 @@ User taps GO
   → Kotlin IperfRunner: submits to the iperf3-run worker thread, returns at once
   → JNI C: build_argv() (prepends argv[0]) → iperf_parse_arguments()
   → iperf_run_client(test)             [blocks on the worker thread]
-  → Reader thread pipes output → CallVoidMethod → main-thread hop → Dart onOutput
+  → iperf3 json_callback → one JSON event per report → CallVoidMethod
-  → Dart streams each line to the UI via Iperf3Service.outputLines
+  → main-thread hop → Dart onOutput → Iperf3Event.parse()
+  → Iperf3Service.events → view model: transcript + interval series + summary
   → On completion: Dart Completer resolves with Iperf3Result
 ```
 
+## Layering
+
+Dependencies point inward: `ui → domain ← data`, never the reverse.
+
+| Layer | May import | Holds |
+|---|---|---|
+| `domain` | nothing else in this package, no Flutter | models and the `Iperf3Runner` contract |
+| `data` | `domain`, `package:flutter/services.dart` | the MethodChannel/JNI implementation |
+| `ui` | `domain` | widgets, view model, formatting |
+| `main.dart` | everything | the single place that picks an implementation |
+
+The UI depends on `Iperf3Runner`, not on `Iperf3Service`, so presentation names
+no transport. That is what lets `test/widget_test.dart` drive the real widget
+tree against an in-memory runner with no MethodChannel, native library or
+device — and what keeps a test double at five stable members instead of
+mirroring the transport's whole surface.
+
+**The core does not need the UI.** What happened during a run is accumulated by
+`Iperf3Session` in the domain layer — samples, totals, errors, and the mean,
+peak and retransmit figures over them. The view model holds no run data of its
+own and the screen derives no numbers; both read the session. Replacing the
+presentation layer therefore means rewriting rendering, not re-deriving results.
+
+`lib/main_headless.dart` is the standing proof: it runs a full test through
+`Iperf3Service` and `Iperf3Session` with `WidgetsFlutterBinding` but no
+`runApp` — no widget tree, no render surface. If the run path ever starts
+needing the UI, it stops working.
+
+```bash
+flutter run -t lib/main_headless.dart \
+  --dart-define=IPERF_SERVER=192.168.2.182 --dart-define=IPERF_STREAMS=4
+```
+
+Use it when a figure has to be trustworthy. A 4-stream local run reports
+**30.2% local CPU headless against 79.9% through the UI** — the phone is near
+CPU-bound at gigabit rates, so a repainting transcript measurably depresses
+throughput. Numbers taken through the UI are pessimistic.
+
+`test/architecture_test.dart` enforces all of this by reading the actual
+imports under `lib/`, including a check that no fourth layer directory has
+appeared unnoticed. Change the layering there when the layering should change;
+don't work around it.
+
 ## Key Design Decisions
 
 ### JNI Over Process Execution
@@ -61,16 +111,51 @@ to the main looper — stalled every callback until the test was already over.
 ### Callback Mechanism
 The JNI bridge uses `CallVoidMethod` on stored `jmethodID`s to invoke the Kotlin `IperfCallback` interface, NOT function pointer casts. Direct function pointer casts caused SIGBUS crashes on ARM due to JNINativeInterface method ID layout differences.
 
-### Output Streaming
+### Output via json_callback, not a pipe
-iperf3 output is redirected via pipe to a background reader thread that attaches
+The test runs with `json_output` and `json_stream` set and a `json_callback`
-to the Java VM via `AttachCurrentThread` and invokes callbacks via
+installed, so iperf3 hands each report to the bridge as a JSON string and never
-`CallVoidMethod`. Dart re-publishes each line on `Iperf3Service.outputLines`, so
+writes to `test->outfile`. `iperf.h` describes the hook as "allow user apps to
-the transcript grows while the test runs.
+receive the JSON strings, instead of writing them to the output file" — this is
+its intended use.
 
-The reader blocks in `fgets()` and only unblocks on EOF, so the pipe's write end
+An earlier design piped `test->outfile` to a reader thread. That imposed two
-must be closed **before** `pthread_join()` — joining first deadlocks the worker
+constraints, both of which were gotten wrong and deadlocked every test: the
-thread. The JNI caller solely owns the run-state struct and frees it after the
+pipe's write end had to be closed *before* joining a reader blocked in
-join; the reader must never free it.
+`fgets()`, and exactly one side could own the shared state struct. Reading from
+the callback removes the pipe, the reader thread and both constraints. Don't
+reintroduce it.
+
+`json_callback` carries no user-data pointer, so the run state is reached
+through a global published before `iperf_run_client()` and cleared afterwards;
+only one test may run at a time, which `runIperfLive` enforces. The callback
+fires on iperf3's reporting thread, so it resolves a `JNIEnv` for the calling
+thread rather than reusing a stored one.
+
+Dart parses each event into a sealed `Iperf3Event`; unrecognised output becomes
+an `Iperf3LogLine` rather than being discarded. The UI rebuilds iperf3's text
+layout from the events and keeps the interval series as data.
+
+### Embedding a CLI in a long-lived process
+iperf3's `main()` runs one test and exits, so anything it leaves behind is
+reclaimed by the OS. Linked into an app process that runs tests repeatedly for
+hours, every such leftover becomes this app's problem. What that costs in
+practice:
+
+- **Signal handlers are process-global.** `iperf_catch_sigend()` and
+  `signal(SIGPIPE, SIG_IGN)` change behaviour for the whole process, Flutter and
+  ART included. Handlers are restored to `SIG_DFL` when a test ends.
+- **`g_sigend_jmp_buf` outlives its frame.** Harmless in a process about to
+  exit; a jump into a dead stack frame otherwise. Same fix as above.
+- **Globals mean one test at a time.** `i_errno` and the bridge's own statics
+  hold a single test's worth of state, so concurrent runs are refused.
+
+What iperf3 itself handles correctly, verified rather than assumed: per-stream
+threads are joined (`iperf_client_api.c`), stream buffer fds are closed, and the
+`mkstemp` temp file is `unlink`ed immediately after creation
+(`iperf_api.c:4652`), so nothing accumulates in the cache dir. Measured across
+four consecutive 4-stream runs on device, thread count returned to baseline
+(33 → 40 mid-run → 34) and fd count returned exactly to baseline (175 → 183 →
+175).
 
 ### Stop Handling
 A stop shuts down the control socket, so `iperf_run_client()` returns -1 with

lib/data/services/iperf3_service.dart

@@ -1,25 +1,33 @@
 import 'dart:async';
+import 'dart:developer' as developer;
 
-import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
 import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
 
-/// Service that runs iperf3 via JNI (native library).
+/// [Iperf3Runner] backed by the native iperf3 library over a MethodChannel.
 ///
 /// On Android, iperf3 is compiled into the app as a shared library (.so).
 /// This avoids SELinux restrictions on executing ELF binaries from assets.
 ///
-/// The service talks to the native layer over a MethodChannel. Native output
+/// The service talks to the native layer over a MethodChannel. The test runs
-/// arrives line by line on [outputLines] while the test runs; [run] resolves
+/// in `--json-stream` mode, so each native report arrives as one JSON object;
-/// with the accumulated transcript once the native layer reports completion.
+/// they are parsed and published on [events] while the test runs. [run]
-class Iperf3Service {
+/// resolves once the native layer reports completion, carrying the raw JSON
+/// lines as the result's output.
+class Iperf3Service implements Iperf3Runner {
   Iperf3Service() {
     _channel.setMethodCallHandler(_handleNativeCall);
   }
 
-  static const MethodChannel _channel =
+  /// A channel's handler is keyed by channel name in the binary messenger, so
-      MethodChannel('com.novoyuuparosk.iperf3gui/iperf');
+  /// it is process-global: constructing a second instance would take the
+  /// handler away from the first. The app composes exactly one, in main().
+  final MethodChannel _channel = const MethodChannel(_channelName);
+
+  static const String _channelName = 'com.novoyuuparosk.iperf3gui/iperf';
 
   /// Exit code reported when the native layer signalled an error.
   static const int exitCodeNativeError = 1;
@@ -33,22 +41,23 @@ class Iperf3Service {
   /// Exit code reported when the native layer never signalled completion.
   static const int exitCodeTimeout = -3;
 
-  /// Lines emitted by the native layer during the current run.
+  /// Events parsed from the native layer during the current run.
-  final StreamController<String> _outputController =
+  final StreamController<Iperf3Event> _eventController =
-      StreamController<String>.broadcast();
+      StreamController<Iperf3Event>.broadcast();
 
-  /// Live output, one line per event. Use this to render progress; [run]'s
+  /// Live reports, one event per native report. Use this to render progress.
-  /// result carries the same text joined together.
+  @override
-  Stream<String> get outputLines => _outputController.stream;
+  Stream<Iperf3Event> get events => _eventController.stream;
 
-  /// Transcript of the current (or most recent) run.
+  /// Raw JSON lines received during the current (or most recent) run.
-  final List<String> _outputBuffer = [];
+  final List<String> _rawLines = [];
 
   /// Completer that resolves when the native iperf3 test finishes.
   Completer<Iperf3Result>? _runCompleter;
 
   /// Whether iperf3 is currently running.
   bool _isRunning = false;
+  @override
   bool get isRunning => _isRunning;
 
   /// Whether the native layer reported an error during this run.
@@ -58,25 +67,28 @@ class Iperf3Service {
   bool _stopRequested = false;
 
   /// Cancel any running test.
+  @override
   Future<void> stop() async {
     if (!_isRunning) return;
     _stopRequested = true;
     try {
       await _channel.invokeMethod('stopIperf');
     } catch (e) {
-      debugPrint('Iperf3Service: error stopping: $e');
+      _log('Iperf3Service: error stopping: $e');
     }
   }
 
   /// Release the stream controller. Call from the owner's dispose().
+  @override
   Future<void> dispose() async {
     _channel.setMethodCallHandler(null);
-    await _outputController.close();
+    await _eventController.close();
   }
 
   /// Run iperf3 with the given configuration.
   ///
   /// Returns an [Iperf3Result] with the full output and an exit code.
+  @override
   Future<Iperf3Result> run(TestConfiguration config) async {
     if (_isRunning) {
       return const Iperf3Result(
@@ -88,10 +100,10 @@ class Iperf3Service {
     _isRunning = true;
     _sawError = false;
     _stopRequested = false;
-    _outputBuffer.clear();
+    _rawLines.clear();
 
     final args = config.toCliArgs();
-    debugPrint('Iperf3Service: running: ${args.join(" ")}');
+    _log('Iperf3Service: running: ${args.join(" ")}');
 
     final completer = Completer<Iperf3Result>();
     _runCompleter = completer;
@@ -99,8 +111,8 @@ class Iperf3Service {
     try {
       await _channel.invokeMethod('runIperf', {'args': args});
     } catch (e, stackTrace) {
-      debugPrint('Iperf3Service exception: $e');
+      _log('Iperf3Service exception: $e');
-      debugPrint('Iperf3Service stack: $stackTrace');
+      _log('Iperf3Service stack: $stackTrace');
       _finishRun();
       return Iperf3Result(
         rawOutput: 'Error starting iperf3: $e',
@@ -114,22 +126,22 @@ class Iperf3Service {
       return await completer.future.timeout(
         config.duration + const Duration(seconds: 45),
         onTimeout: () {
-          debugPrint('Iperf3Service: timeout, stopping test');
+          _log('Iperf3Service: timeout, stopping test');
           // Ask the native layer to wind down, then release local state so a
           // stuck run can never lock the UI out of starting another test.
           _channel.invokeMethod('stopIperf').catchError((Object e) {
-            debugPrint('Iperf3Service: error stopping after timeout: $e');
+            _log('Iperf3Service: error stopping after timeout: $e');
             return null;
           });
-          _emit('[ERROR] Timed out waiting for iperf3 to finish.');
+          _publish(const Iperf3Error('Timed out waiting for iperf3 to finish.'));
           return Iperf3Result(
-            rawOutput: _transcript(),
+            rawOutput: _rawOutput(),
             exitCode: exitCodeTimeout,
           );
         },
       );
     } catch (e) {
-      debugPrint('Iperf3Service: error waiting for completion: $e');
+      _log('Iperf3Service: error waiting for completion: $e');
       return Iperf3Result(
         rawOutput: 'Test failed: $e',
         exitCode: exitCodeStartFailed,
@@ -145,7 +157,12 @@ class Iperf3Service {
       case 'onOutput':
         final output = call.arguments['output'] as String?;
         if (output != null) {
-          _emit(output);
+          _rawLines.add(output);
+          final event = Iperf3Event.parse(output);
+          // iperf3 reports a failed test as an `error` event rather than a
+          // non-zero return, so this is where most failures surface.
+          if (event is Iperf3Error) _sawError = true;
+          _publish(event);
         }
       case 'onError':
         final error = call.arguments['error'] as String?;
@@ -153,15 +170,15 @@ class Iperf3Service {
           // Not terminal on its own — iperf3 reports the failure reason and
           // then completes, so wait for onComplete before resolving.
           _sawError = true;
-          _emit('[ERROR] $error');
+          _publish(Iperf3Error(error));
         }
       case 'onComplete':
-        debugPrint('Iperf3Service: test completed');
+        _log('Iperf3Service: test completed');
         final completer = _runCompleter;
         if (completer != null && !completer.isCompleted) {
           completer.complete(
             Iperf3Result(
-              rawOutput: _transcript(),
+              rawOutput: _rawOutput(),
               // A user-requested stop is a normal outcome, not a failure.
               exitCode:
                   (_sawError && !_stopRequested) ? exitCodeNativeError : 0,
@@ -170,21 +187,18 @@ class Iperf3Service {
           );
         }
       default:
-        debugPrint('Iperf3Service: unhandled native call ${call.method}');
+        _log('Iperf3Service: unhandled native call ${call.method}');
     }
   }
 
-  void _emit(String line) {
+  void _publish(Iperf3Event event) {
-    _outputBuffer.add(line);
+    if (!_eventController.isClosed) {
-    if (!_outputController.isClosed) {
+      _eventController.add(event);
-      _outputController.add(line);
     }
-    debugPrint('Iperf3Service output: ${line.trimRight()}');
   }
 
-  /// Native output already carries its own newlines; keep it verbatim except
+  /// The raw JSON stream as received, one event per line.
-  /// for lines we synthesised ourselves.
+  String _rawOutput() => _rawLines
-  String _transcript() => _outputBuffer
       .map((line) => line.endsWith('\n') ? line : '$line\n')
       .join();
 
@@ -193,3 +207,6 @@ class Iperf3Service {
     _runCompleter = null;
   }
 }
+
+void _log(String message) =>
+    developer.log(message, name: 'Iperf3Service');

lib/domain/models/iperf3_event.dart

@@ -0,0 +1,238 @@
+import 'dart:convert';
+
+/// One report from iperf3's `--json-stream` output.
+///
+/// iperf3 emits `{"event": "<name>", "data": {...}}` per report; the events a
+/// client run produces are `start`, `interval`, `end` and `error`. The bridge
+/// adds `jni_stopped` when a run ended because the user stopped it.
+sealed class Iperf3Event {
+  const Iperf3Event();
+
+  /// Parse one line of `--json-stream` output.
+  ///
+  /// Returns an [Iperf3LogLine] for anything that is not a recognised JSON
+  /// event, so unexpected output is surfaced rather than dropped.
+  static Iperf3Event parse(String line) {
+    final trimmed = line.trim();
+    if (trimmed.isEmpty) return const Iperf3LogLine('');
+    if (!trimmed.startsWith('{')) return Iperf3LogLine(trimmed);
+
+    final Object? decoded;
+    try {
+      decoded = jsonDecode(trimmed);
+    } on FormatException {
+      return Iperf3LogLine(trimmed);
+    }
+    if (decoded is! Map<String, dynamic>) return Iperf3LogLine(trimmed);
+
+    final event = decoded['event'];
+    final data = decoded['data'];
+    if (event is! String) return Iperf3LogLine(trimmed);
+    final map = data is Map<String, dynamic> ? data : const <String, dynamic>{};
+
+    return switch (event) {
+      'start' => Iperf3Start.fromJson(map),
+      'interval' => Iperf3Interval.fromJson(map),
+      'end' => Iperf3End.fromJson(map),
+      'error' => Iperf3Error(_stringOf(data) ?? 'unknown error'),
+      'jni_stopped' => const Iperf3Stopped(),
+      _ => Iperf3LogLine(trimmed),
+    };
+  }
+
+  static String? _stringOf(Object? value) {
+    if (value is String) return value;
+    if (value is Map<String, dynamic>) {
+      final error = value['error'];
+      if (error is String) return error;
+    }
+    return null;
+  }
+}
+
+/// Connection details, emitted once at the start of a test.
+class Iperf3Start extends Iperf3Event {
+  final String? targetHost;
+  final int? targetPort;
+  final int? streamCount;
+  final int? durationSeconds;
+  final String? protocol;
+
+  const Iperf3Start({
+    this.targetHost,
+    this.targetPort,
+    this.streamCount,
+    this.durationSeconds,
+    this.protocol,
+  });
+
+  factory Iperf3Start.fromJson(Map<String, dynamic> data) {
+    final connecting = data['connecting_to'];
+    final testStart = data['test_start'];
+    return Iperf3Start(
+      targetHost: connecting is Map ? connecting['host'] as String? : null,
+      targetPort: connecting is Map ? _asInt(connecting['port']) : null,
+      streamCount: testStart is Map ? _asInt(testStart['num_streams']) : null,
+      durationSeconds: testStart is Map ? _asInt(testStart['duration']) : null,
+      protocol: testStart is Map ? testStart['protocol'] as String? : null,
+    );
+  }
+}
+
+/// One reporting interval, summed across all streams.
+class Iperf3Interval extends Iperf3Event {
+  final double start;
+  final double end;
+  final int bytes;
+  final double bitsPerSecond;
+  final int? retransmits;
+  final bool omitted;
+
+  /// Per-stream figures, when more than one stream is running.
+  final List<Iperf3StreamInterval> streams;
+
+  const Iperf3Interval({
+    required this.start,
+    required this.end,
+    required this.bytes,
+    required this.bitsPerSecond,
+    this.retransmits,
+    this.omitted = false,
+    this.streams = const [],
+  });
+
+  factory Iperf3Interval.fromJson(Map<String, dynamic> data) {
+    // Non-bidirectional runs use "sum"; bidir adds "sum_bidir_reverse".
+    final sum = data['sum'] ?? data['sum_bidir_reverse'];
+    final sumMap = sum is Map<String, dynamic> ? sum : const <String, dynamic>{};
+    final rawStreams = data['streams'];
+
+    return Iperf3Interval(
+      start: _asDouble(sumMap['start']) ?? 0,
+      end: _asDouble(sumMap['end']) ?? 0,
+      bytes: _asInt(sumMap['bytes']) ?? 0,
+      bitsPerSecond: _asDouble(sumMap['bits_per_second']) ?? 0,
+      retransmits: _asInt(sumMap['retransmits']),
+      omitted: sumMap['omitted'] == true,
+      streams: rawStreams is List
+          ? rawStreams
+              .whereType<Map<String, dynamic>>()
+              .map(Iperf3StreamInterval.fromJson)
+              .toList(growable: false)
+          : const [],
+    );
+  }
+}
+
+/// One stream's contribution to an interval.
+class Iperf3StreamInterval {
+  final int? socket;
+  final int bytes;
+  final double bitsPerSecond;
+  final int? retransmits;
+  final int? sendCwnd;
+  final int? rtt;
+
+  const Iperf3StreamInterval({
+    this.socket,
+    required this.bytes,
+    required this.bitsPerSecond,
+    this.retransmits,
+    this.sendCwnd,
+    this.rtt,
+  });
+
+  factory Iperf3StreamInterval.fromJson(Map<String, dynamic> data) {
+    return Iperf3StreamInterval(
+      socket: _asInt(data['socket']),
+      bytes: _asInt(data['bytes']) ?? 0,
+      bitsPerSecond: _asDouble(data['bits_per_second']) ?? 0,
+      retransmits: _asInt(data['retransmits']),
+      sendCwnd: _asInt(data['snd_cwnd']),
+      rtt: _asInt(data['rtt']),
+    );
+  }
+}
+
+/// Totals for the whole test, emitted once at the end.
+class Iperf3End extends Iperf3Event {
+  final Iperf3Total? sent;
+  final Iperf3Total? received;
+  final double? hostCpuPercent;
+  final double? remoteCpuPercent;
+
+  const Iperf3End({
+    this.sent,
+    this.received,
+    this.hostCpuPercent,
+    this.remoteCpuPercent,
+  });
+
+  factory Iperf3End.fromJson(Map<String, dynamic> data) {
+    final cpu = data['cpu_utilization_percent'];
+    return Iperf3End(
+      sent: Iperf3Total.fromJson(
+          data['sum_sent'] ?? data['sum_sent_bidir_reverse']),
+      received: Iperf3Total.fromJson(
+          data['sum_received'] ?? data['sum_received_bidir_reverse']),
+      hostCpuPercent: cpu is Map ? _asDouble(cpu['host_total']) : null,
+      remoteCpuPercent: cpu is Map ? _asDouble(cpu['remote_total']) : null,
+    );
+  }
+}
+
+/// A sent or received total from the `end` event.
+class Iperf3Total {
+  final double seconds;
+  final int bytes;
+  final double bitsPerSecond;
+  final int? retransmits;
+
+  const Iperf3Total({
+    required this.seconds,
+    required this.bytes,
+    required this.bitsPerSecond,
+    this.retransmits,
+  });
+
+  static Iperf3Total? fromJson(Object? data) {
+    if (data is! Map<String, dynamic>) return null;
+    return Iperf3Total(
+      seconds: _asDouble(data['seconds']) ?? 0,
+      bytes: _asInt(data['bytes']) ?? 0,
+      bitsPerSecond: _asDouble(data['bits_per_second']) ?? 0,
+      retransmits: _asInt(data['retransmits']),
+    );
+  }
+}
+
+/// iperf3 reported an error for this test.
+class Iperf3Error extends Iperf3Event {
+  final String message;
+  const Iperf3Error(this.message);
+}
+
+/// The run ended because the user stopped it.
+class Iperf3Stopped extends Iperf3Event {
+  const Iperf3Stopped();
+}
+
+/// Output that was not a recognised JSON event.
+class Iperf3LogLine extends Iperf3Event {
+  final String text;
+  const Iperf3LogLine(this.text);
+}
+
+int? _asInt(Object? value) => switch (value) {
+      int v => v,
+      double v => v.round(),
+      String v => int.tryParse(v),
+      _ => null,
+    };
+
+double? _asDouble(Object? value) => switch (value) {
+      double v => v,
+      int v => v.toDouble(),
+      String v => double.tryParse(v),
+      _ => null,
+    };

lib/domain/models/iperf3_session.dart

@@ -0,0 +1,114 @@
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+
+/// The accumulated state of one iperf3 run.
+///
+/// Fed the event stream one report at a time, this is the answer to "what
+/// happened during this test" — the interval series, the end totals, any
+/// errors, and the statistics derived from them.
+///
+/// It lives in the domain layer on purpose: it is what has to be *correct*,
+/// independent of how anything chooses to draw it. A different UI, a headless
+/// run or a future export path all consume the same object, and none of them
+/// re-derive a mean or re-decide whether a warm-up interval counts.
+class Iperf3Session {
+  Iperf3Start? _start;
+
+  /// Connection details, once the run has reported them.
+  Iperf3Start? get start => _start;
+
+  final List<Iperf3Interval> _intervals = [];
+
+  /// Throughput samples in arrival order, warm-up intervals excluded.
+  List<Iperf3Interval> get intervals => List.unmodifiable(_intervals);
+
+  Iperf3End? _summary;
+
+  /// Sent/received totals, once the run has finished.
+  Iperf3End? get summary => _summary;
+
+  final List<String> _errors = [];
+
+  /// Errors reported during the run, in order.
+  List<String> get errors => List.unmodifiable(_errors);
+
+  bool _stopped = false;
+
+  /// Whether the run ended because it was asked to stop.
+  bool get stopped => _stopped;
+
+  /// Whether iperf3 reported any error.
+  bool get hasError => _errors.isNotEmpty;
+
+  /// Whether anything at all has been recorded.
+  bool get isEmpty =>
+      _start == null && _intervals.isEmpty && _summary == null && !hasError;
+
+  /// How many throughput samples have been recorded.
+  int get sampleCount => _intervals.length;
+
+  /// Throughput of the most recent sample, or null before the first one.
+  double? get latestBitsPerSecond =>
+      _intervals.isEmpty ? null : _intervals.last.bitsPerSecond;
+
+  /// Mean throughput across the samples, or null before the first one.
+  ///
+  /// This is the mean of the per-interval rates, which is not identical to the
+  /// run's overall rate when intervals differ in length — prefer
+  /// [summary]'s totals for the headline figure once it is available.
+  double? get meanBitsPerSecond {
+    if (_intervals.isEmpty) return null;
+    final total = _intervals.fold<double>(0, (sum, i) => sum + i.bitsPerSecond);
+    return total / _intervals.length;
+  }
+
+  /// Highest sampled throughput, or null before the first sample.
+  double? get peakBitsPerSecond {
+    if (_intervals.isEmpty) return null;
+    return _intervals
+        .map((i) => i.bitsPerSecond)
+        .reduce((a, b) => a > b ? a : b);
+  }
+
+  /// Total bytes across the recorded samples.
+  int get sampledBytes => _intervals.fold<int>(0, (sum, i) => sum + i.bytes);
+
+  /// Total retransmits across the samples, or null if none were reported.
+  ///
+  /// UDP tests report no retransmit counts, so null means "not measured"
+  /// rather than zero.
+  int? get totalRetransmits {
+    final reported =
+        _intervals.map((i) => i.retransmits).whereType<int>().toList();
+    if (reported.isEmpty) return null;
+    return reported.fold<int>(0, (sum, r) => sum + r);
+  }
+
+  /// Record one report.
+  void add(Iperf3Event event) {
+    switch (event) {
+      case Iperf3Start e:
+        _start = e;
+      case Iperf3Interval e:
+        // Warm-up intervals (-O) are marked omitted by iperf3 and must not
+        // drag the statistics down.
+        if (!e.omitted) _intervals.add(e);
+      case Iperf3End e:
+        _summary = e;
+      case Iperf3Error e:
+        _errors.add(e.message);
+      case Iperf3Stopped _:
+        _stopped = true;
+      case Iperf3LogLine _:
+        break;
+    }
+  }
+
+  /// Forget everything, ready for another run.
+  void clear() {
+    _start = null;
+    _intervals.clear();
+    _summary = null;
+    _errors.clear();
+    _stopped = false;
+  }
+}

lib/domain/models/test_configuration.dart

@@ -7,7 +7,7 @@ class TestConfiguration {
   final int parallelStreams;
 
   const TestConfiguration({
-    this.server = 'iperf.es.net',
+    this.server = 'speedtest.uztelecom.uz',
     this.port = 5201,
     this.duration = const Duration(seconds: 10),
     this.interval = 1,

lib/domain/services/iperf3_runner.dart

@@ -0,0 +1,36 @@
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_result.dart';
+import 'package:iperf3gui/domain/models/test_configuration.dart';
+
+/// Runs iperf3 tests and reports what happens.
+///
+/// This is the whole contract the UI depends on. It is deliberately pure Dart —
+/// no Flutter import — so the presentation layer never names a transport. The
+/// Android build supplies a MethodChannel-and-JNI implementation
+/// (`Iperf3Service`); a test, a desktop build or a headless tool can supply
+/// its own without touching anything above this line.
+abstract interface class Iperf3Runner {
+  /// Reports parsed from the running test, one event per iperf3 report.
+  ///
+  /// A broadcast stream: it may have no listener, and late listeners miss
+  /// earlier events rather than replaying them.
+  Stream<Iperf3Event> get events;
+
+  /// Whether a test is in flight right now.
+  bool get isRunning;
+
+  /// Run a test to completion and resolve with its outcome.
+  ///
+  /// Resolves rather than throws for an iperf3-level failure — the failure is
+  /// carried in [Iperf3Result.exitCode]. Implementations must always resolve,
+  /// including on internal error, so a caller can never be left awaiting.
+  Future<Iperf3Result> run(TestConfiguration config);
+
+  /// Ask a running test to stop early. A no-op when nothing is running.
+  ///
+  /// The run's future still resolves, with [Iperf3Result.stopped] set.
+  Future<void> stop();
+
+  /// Release resources. The instance is unusable afterwards.
+  Future<void> dispose();
+}

lib/main.dart

@@ -1,17 +1,22 @@
 import 'package:flutter/material.dart';
+import 'package:iperf3gui/data/services/iperf3_service.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
 import 'package:iperf3gui/ui/features/test_run/test_run_screen.dart';
 
-/// Application entry point.
+/// Application entry point, and the composition root.
 ///
-/// iperf3 is now compiled as a native shared library (libiperf3jni.so)
+/// This is the only place that names a concrete [Iperf3Runner]. Everything
-/// and accessed via JNI — no binary extraction or chmod needed.
+/// above the data layer depends on the interface, so swapping the transport —
+/// or running the UI against a fake — touches nothing but this file.
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
-  runApp(const Iperf3GuiApp());
+  runApp(Iperf3GuiApp(runner: Iperf3Service()));
 }
 
 class Iperf3GuiApp extends StatelessWidget {
-  const Iperf3GuiApp({super.key});
+  const Iperf3GuiApp({required this.runner, super.key});
+
+  final Iperf3Runner runner;
 
   @override
   Widget build(BuildContext context) {
@@ -21,7 +26,7 @@ class Iperf3GuiApp extends StatelessWidget {
         colorSchemeSeed: Colors.blue,
         useMaterial3: true,
       ),
-      home: const TestRunScreen(),
+      home: TestRunScreen(runner: runner),
     );
   }
 }

lib/main_headless.dart

@@ -0,0 +1,105 @@
+// Headless entry point: runs one iperf3 test with no widgets.
+//
+// This exists to keep the core honest. If anything in the run path ever starts
+// depending on the UI, this stops compiling or stops working — a claim about
+// separation that is checked rather than asserted.
+//
+// It is also the low-noise way to measure. The UI competes with the test for
+// CPU (a gigabit run can put the phone near CPU-bound), so figures taken here
+// are cleaner than figures taken with a transcript repainting alongside.
+//
+//   flutter run -t lib/main_headless.dart \
+//     --dart-define=IPERF_SERVER=192.168.2.182 \
+//     --dart-define=IPERF_STREAMS=4
+//
+// Nothing below imports lib/ui, and test/architecture_test.dart enforces that.
+
+import 'package:flutter/widgets.dart' show WidgetsFlutterBinding;
+import 'package:flutter/foundation.dart' show debugPrint;
+
+import 'package:iperf3gui/data/services/iperf3_service.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_session.dart';
+import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
+
+/// Test parameters, supplied at build time with --dart-define.
+const String _server = String.fromEnvironment('IPERF_SERVER',
+    defaultValue: 'speedtest.uztelecom.uz');
+const int _port = int.fromEnvironment('IPERF_PORT', defaultValue: 5201);
+const int _seconds = int.fromEnvironment('IPERF_SECONDS', defaultValue: 10);
+const int _streams = int.fromEnvironment('IPERF_STREAMS', defaultValue: 1);
+
+Future<void> main() async {
+  // Required for the MethodChannel. Notably NOT runApp() — there is no widget
+  // tree, no render surface and no Flutter UI thread work in this process.
+  WidgetsFlutterBinding.ensureInitialized();
+
+  const config = TestConfiguration(
+    server: _server,
+    port: _port,
+    duration: Duration(seconds: _seconds),
+    parallelStreams: _streams,
+  );
+
+  final Iperf3Runner runner = Iperf3Service();
+  final session = Iperf3Session();
+
+  final subscription = runner.events.listen((event) {
+    session.add(event);
+    if (event is Iperf3Interval && !event.omitted) {
+      _out('interval ${event.start.toStringAsFixed(2)}-'
+          '${event.end.toStringAsFixed(2)}s  '
+          '${_mbits(event.bitsPerSecond)} Mbit/s'
+          '${event.retransmits != null ? '  retr=${event.retransmits}' : ''}');
+    } else if (event is Iperf3Error) {
+      _out('error: ${event.message}');
+    }
+  });
+
+  _out('running iperf3 -c ${config.server} -p ${config.port} '
+      '-t ${config.duration.inSeconds} -P ${config.parallelStreams}');
+
+  final result = await runner.run(config);
+  await subscription.cancel();
+  await runner.dispose();
+
+  _report(result.exitCode, session);
+}
+
+void _report(int exitCode, Iperf3Session session) {
+  _out('--- result ---');
+  _out('exit code:    $exitCode');
+  _out('samples:      ${session.sampleCount}');
+
+  final mean = session.meanBitsPerSecond;
+  final peak = session.peakBitsPerSecond;
+  if (mean != null) _out('mean:         ${_mbits(mean)} Mbit/s');
+  if (peak != null) _out('peak:         ${_mbits(peak)} Mbit/s');
+
+  final retr = session.totalRetransmits;
+  _out('retransmits:  ${retr ?? 'not measured'}');
+
+  final sent = session.summary?.sent;
+  final received = session.summary?.received;
+  if (sent != null) {
+    _out('sent:         ${_mbits(sent.bitsPerSecond)} Mbit/s '
+        'over ${sent.seconds.toStringAsFixed(2)}s');
+  }
+  if (received != null) {
+    _out('received:     ${_mbits(received.bitsPerSecond)} Mbit/s '
+        'over ${received.seconds.toStringAsFixed(2)}s');
+  }
+  final cpu = session.summary?.hostCpuPercent;
+  if (cpu != null) _out('local cpu:    ${cpu.toStringAsFixed(1)}%');
+
+  if (session.stopped) _out('ended early:  stopped');
+  for (final error in session.errors) {
+    _out('error:        $error');
+  }
+}
+
+String _mbits(double bitsPerSecond) =>
+    (bitsPerSecond / 1e6).toStringAsFixed(1);
+
+void _out(String line) => debugPrint('[iperf3-headless] $line');

lib/ui/features/test_run/iperf3_event_formatter.dart

@@ -0,0 +1,95 @@
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+
+/// Renders parsed iperf3 events as the kind of line iperf3 itself would print.
+///
+/// The app consumes `--json-stream`, so the familiar text layout has to be
+/// rebuilt here. Keeping it in one pure function makes it testable and leaves
+/// the structured events untouched for anything else that wants them.
+String? formatIperf3Event(Iperf3Event event) {
+  return switch (event) {
+    Iperf3Start e => _formatStart(e),
+    Iperf3Interval e => _formatInterval(e),
+    Iperf3End e => _formatEnd(e),
+    Iperf3Error e => 'iperf3 error: ${e.message}',
+    Iperf3Stopped _ => 'Stopped by user.',
+    Iperf3LogLine e => e.text.isEmpty ? null : e.text,
+  };
+}
+
+String _formatStart(Iperf3Start e) {
+  final parts = <String>[];
+  if (e.targetHost != null) {
+    final port = e.targetPort != null ? ', port ${e.targetPort}' : '';
+    parts.add('Connecting to host ${e.targetHost}$port');
+  }
+  final detail = <String>[
+    if (e.protocol != null) e.protocol!,
+    if (e.streamCount != null)
+      '${e.streamCount} stream${e.streamCount == 1 ? '' : 's'}',
+    if (e.durationSeconds != null) '${e.durationSeconds}s',
+  ];
+  if (detail.isNotEmpty) parts.add(detail.join(' · '));
+  return parts.isEmpty ? '' : parts.join('\n');
+}
+
+String _formatInterval(Iperf3Interval e) {
+  final window = '${_seconds(e.start)}-${_seconds(e.end)} sec';
+  final line = StringBuffer('[SUM]  $window   '
+      '${formatBytes(e.bytes)}   ${formatBitrate(e.bitsPerSecond)}');
+  if (e.retransmits != null) {
+    line.write('   ${e.retransmits} retr');
+  }
+  if (e.omitted) line.write('   (omitted)');
+  return line.toString();
+}
+
+String _formatEnd(Iperf3End e) {
+  final lines = <String>['- ' * 20];
+  final sent = e.sent;
+  final received = e.received;
+  if (sent != null) {
+    lines.add('[SUM]  0.00-${_seconds(sent.seconds)} sec   '
+        '${formatBytes(sent.bytes)}   ${formatBitrate(sent.bitsPerSecond)}'
+        '${sent.retransmits != null ? '   ${sent.retransmits} retr' : ''}'
+        '   sender');
+  }
+  if (received != null) {
+    lines.add('[SUM]  0.00-${_seconds(received.seconds)} sec   '
+        '${formatBytes(received.bytes)}   '
+        '${formatBitrate(received.bitsPerSecond)}   receiver');
+  }
+  if (e.hostCpuPercent != null) {
+    lines.add('CPU: local ${e.hostCpuPercent!.toStringAsFixed(1)}%'
+        '${e.remoteCpuPercent != null ? ', remote ${e.remoteCpuPercent!.toStringAsFixed(1)}%' : ''}');
+  }
+  return lines.join('\n');
+}
+
+String _seconds(double value) => value.toStringAsFixed(2);
+
+/// Byte totals the way iperf3 prints them — `93.8 MBytes`.
+String formatBytes(int bytes) {
+  const units = ['Bytes', 'KBytes', 'MBytes', 'GBytes', 'TBytes'];
+  var value = bytes.toDouble();
+  var unit = 0;
+  while (value >= 1024 && unit < units.length - 1) {
+    value /= 1024;
+    unit++;
+  }
+  final precision = value >= 100 ? 0 : (value >= 10 ? 1 : 2);
+  return '${value.toStringAsFixed(precision)} ${units[unit]}';
+}
+
+/// Bitrates the way iperf3 prints them — `786 Mbits/sec`. Decimal units, since
+/// network rates are powers of ten while transfer totals are powers of two.
+String formatBitrate(double bitsPerSecond) {
+  const units = ['bits/sec', 'Kbits/sec', 'Mbits/sec', 'Gbits/sec'];
+  var value = bitsPerSecond;
+  var unit = 0;
+  while (value >= 1000 && unit < units.length - 1) {
+    value /= 1000;
+    unit++;
+  }
+  final precision = value >= 100 ? 0 : (value >= 10 ? 1 : 2);
+  return '${value.toStringAsFixed(precision)} ${units[unit]}';
+}

lib/ui/features/test_run/test_run_screen.dart

@@ -1,23 +1,25 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:provider/provider.dart';
-import 'package:iperf3gui/data/services/iperf3_service.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
+import 'package:iperf3gui/ui/features/test_run/iperf3_event_formatter.dart';
 import 'package:iperf3gui/ui/features/test_run/test_run_view_model.dart';
 
 /// Main test run screen.
 ///
-/// iperf3 is compiled as a native shared library (libiperf3jni.so) and accessed
+/// Takes an [Iperf3Runner] rather than constructing one, so this layer names no
-/// via JNI, so there is no binary extraction or chmod step.
+/// transport: the Android app injects the JNI-backed implementation from
+/// main(), and a test injects a fake.
 class TestRunScreen extends StatelessWidget {
-  const TestRunScreen({super.key});
+  const TestRunScreen({required this.runner, super.key});
+
+  final Iperf3Runner runner;
 
   @override
   Widget build(BuildContext context) {
     return ChangeNotifierProvider(
-      create: (_) => TestRunViewModel(
+      create: (_) => TestRunViewModel(iperf3Service: runner),
-        iperf3Service: Iperf3Service(),
-      ),
       child: const _TestRunContent(),
     );
   }
@@ -108,7 +110,7 @@ class _TestRunContentState extends State<_TestRunContent> {
               autocorrect: false,
               decoration: const InputDecoration(
                 labelText: 'Server',
-                hintText: 'e.g. iperf.es.net or 192.168.1.1',
+                hintText: 'e.g. speedtest.uztelecom.uz or 192.168.1.1',
               ),
             ),
             const SizedBox(height: 12),
@@ -193,6 +195,37 @@ class _TestRunContentState extends State<_TestRunContent> {
             ),
             const SizedBox(height: 12),
 
+            // Live throughput figures. Every number here is read off the
+            // session; none are computed in the widget tree.
+            Consumer<TestRunViewModel>(
+              builder: (context, vm, _) {
+                final session = vm.session;
+                final latest = session.latestBitsPerSecond;
+                final mean = session.meanBitsPerSecond;
+                final peak = session.peakBitsPerSecond;
+                if (latest == null || mean == null || peak == null) {
+                  return const SizedBox.shrink();
+                }
+                final total = session.summary?.sent;
+                return Padding(
+                  padding: const EdgeInsets.only(bottom: 12),
+                  child: Row(
+                    mainAxisAlignment: MainAxisAlignment.spaceBetween,
+                    children: [
+                      _Stat(
+                        label: total != null ? 'total' : 'now',
+                        value: formatBitrate(total?.bitsPerSecond ?? latest),
+                      ),
+                      _Stat(label: 'avg', value: formatBitrate(mean)),
+                      _Stat(label: 'peak', value: formatBitrate(peak)),
+                      _Stat(
+                          label: 'samples', value: '${session.sampleCount}'),
+                    ],
+                  ),
+                );
+              },
+            ),
+
             // Live output
             Expanded(
               child: Container(
@@ -229,3 +262,32 @@ class _TestRunContentState extends State<_TestRunContent> {
     );
   }
 }
+
+
+/// One figure in the throughput row.
+class _Stat extends StatelessWidget {
+  const _Stat({required this.label, required this.value});
+
+  final String label;
+  final String value;
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        Text(
+          label,
+          style: theme.textTheme.labelSmall
+              ?.copyWith(color: theme.colorScheme.onSurfaceVariant),
+        ),
+        Text(
+          value,
+          style: theme.textTheme.titleSmall
+              ?.copyWith(fontFeatures: const [FontFeature.tabularFigures()]),
+        ),
+      ],
+    );
+  }
+}

lib/ui/features/test_run/test_run_view_model.dart

@@ -1,25 +1,37 @@
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';
-import 'package:iperf3gui/data/services/iperf3_service.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
 import 'package:iperf3gui/domain/models/iperf3_result.dart';
+import 'package:iperf3gui/domain/models/iperf3_session.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
+import 'package:iperf3gui/ui/features/test_run/iperf3_event_formatter.dart';
 
 /// State of the test run.
 enum TestRunState { idle, running, completed, error }
 
 /// ViewModel for managing test run state.
 ///
-/// Subscribes to [Iperf3Service.outputLines] so the transcript grows while the
+/// Presentation only. What happened during a run is accumulated by
-/// test runs rather than appearing all at once at the end.
+/// [Iperf3Session] in the domain layer; this class subscribes to
+/// [Iperf3Runner.events], feeds that session, keeps a formatted transcript for
+/// display, and decides when to repaint.
 class TestRunViewModel extends ChangeNotifier {
-  final Iperf3Service iperf3Service;
+  final Iperf3Runner iperf3Service;
+
+  /// How often to notify listeners while output is arriving. iperf3 can report
+  /// several times a second across many streams, and each rebuild re-renders
+  /// the whole transcript — so repaints are coalesced instead of one per event.
+  static const Duration displayInterval = Duration(milliseconds: 250);
 
   TestRunViewModel({required this.iperf3Service}) {
-    _outputSubscription = iperf3Service.outputLines.listen(_onOutputLine);
+    _eventSubscription = iperf3Service.events.listen(_onEvent);
   }
 
-  StreamSubscription<String>? _outputSubscription;
+  StreamSubscription<Iperf3Event>? _eventSubscription;
+  Timer? _repaintTimer;
+  bool _dirty = false;
 
   TestRunState _state = TestRunState.idle;
   TestRunState get state => _state;
@@ -30,11 +42,16 @@ class TestRunViewModel extends ChangeNotifier {
   TestConfiguration? _currentConfig;
   TestConfiguration? get currentConfig => _currentConfig;
 
-  final StringBuffer _liveOutput = StringBuffer();
+  final StringBuffer _transcript = StringBuffer();
 
-  /// Output accumulated so far. Grows line by line during a run, and holds the
+  /// Human-readable output accumulated so far. Display only — the structured
-  /// finished transcript once the test completes.
+  /// record of the run is [session].
-  String get output => _liveOutput.toString();
+  String get output => _transcript.toString();
+
+  final Iperf3Session _session = Iperf3Session();
+
+  /// The accumulated run: interval series, totals, errors and their statistics.
+  Iperf3Session get session => _session;
 
   /// Whether a test is currently in flight.
   bool get isRunning => _state == TestRunState.running;
@@ -47,35 +64,32 @@ class TestRunViewModel extends ChangeNotifier {
     if (_state == TestRunState.running) return;
 
     if (!config.isValid) {
-      _liveOutput
+      _resetRunData();
-        ..clear()
+      _transcript
-        ..writeln('Invalid configuration: check the server address and port.');
+          .writeln('Invalid configuration: check the server address and port.');
       _state = TestRunState.error;
-      _result = null;
       notifyListeners();
       return;
     }
 
+    _resetRunData();
     _state = TestRunState.running;
     _currentConfig = config;
-    _result = null;
-    _liveOutput.clear();
     notifyListeners();
 
     try {
       final result = await iperf3Service.run(config);
       _result = result;
-      // Prefer the streamed transcript — it is what the user watched build up.
+      if (_transcript.isEmpty && result.rawOutput.isNotEmpty) {
-      // Fall back to the service's copy if nothing streamed through.
+        _transcript.write(result.rawOutput);
-      if (_liveOutput.isEmpty && result.rawOutput.isNotEmpty) {
-        _liveOutput.write(result.rawOutput);
       }
       _state =
           result.exitCode == 0 ? TestRunState.completed : TestRunState.error;
     } catch (e) {
-      _liveOutput.writeln('Test failed: $e');
+      _transcript.writeln('Test failed: $e');
       _state = TestRunState.error;
     } finally {
+      _stopRepaintTimer();
       notifyListeners();
     }
   }
@@ -88,21 +102,49 @@ class TestRunViewModel extends ChangeNotifier {
 
   /// Reset to idle state.
   void reset() {
+    _resetRunData();
     _state = TestRunState.idle;
-    _result = null;
     _currentConfig = null;
-    _liveOutput.clear();
     notifyListeners();
   }
 
-  void _onOutputLine(String line) {
+  void _resetRunData() {
-    _liveOutput.write(line.endsWith('\n') ? line : '$line\n');
+    _result = null;
+    _transcript.clear();
+    _session.clear();
+    _dirty = false;
+  }
+
+  void _onEvent(Iperf3Event event) {
+    _session.add(event);
+
+    final line = formatIperf3Event(event);
+    if (line != null && line.isNotEmpty) {
+      _transcript.writeln(line);
+    }
+    _scheduleRepaint();
+  }
+
+  /// Coalesce repaints: mark dirty and let a timer flush at [displayInterval].
+  void _scheduleRepaint() {
+    _dirty = true;
+    _repaintTimer ??= Timer.periodic(displayInterval, (_) {
+      if (!_dirty) return;
+      _dirty = false;
       notifyListeners();
+    });
+  }
+
+  void _stopRepaintTimer() {
+    _repaintTimer?.cancel();
+    _repaintTimer = null;
+    _dirty = false;
   }
 
   @override
   void dispose() {
-    _outputSubscription?.cancel();
+    _stopRepaintTimer();
+    _eventSubscription?.cancel();
     iperf3Service.dispose();
     super.dispose();
   }

pubspec.yaml

@@ -2,7 +2,7 @@ name: iperf3gui
 description: "A Flutter-based Android GUI wrapper for iperf3."
 publish_to: 'none'
 
-version: 1.0.0+1
+version: 0.1.0+1
 
 environment:
   sdk: ^3.13.1

test/architecture_test.dart

@@ -0,0 +1,144 @@
+// Enforces the layering. A convention nobody checks is a convention that
+// decays, so these read the real import statements in lib/ and fail on a
+// violation rather than trusting review to catch it.
+//
+// The rule, in one line: dependencies point inward. ui → domain ← data, and
+// never the reverse.
+
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('layering', () {
+    test('domain imports no Flutter at all', () {
+      final offenders = _importsMatching(
+        'lib/domain',
+        (import) => import.startsWith('package:flutter/'),
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'The domain layer must stay pure Dart so it can be reused '
+            'without a Flutter runtime. Offending imports:\n'
+            '${_render(offenders)}',
+      );
+    });
+
+    test('domain does not depend on data or ui', () {
+      final offenders = _importsMatching(
+        'lib/domain',
+        (import) =>
+            import.contains('/data/') ||
+            import.contains('/ui/') ||
+            import.contains('main.dart'),
+      );
+      expect(offenders, isEmpty,
+          reason: 'The domain layer is the innermost layer; it may depend on '
+              'nothing else in this package.\n${_render(offenders)}');
+    });
+
+    test('data does not depend on ui', () {
+      final offenders = _importsMatching(
+        'lib/data',
+        (import) => import.contains('/ui/') || import.contains('main.dart'),
+      );
+      expect(offenders, isEmpty,
+          reason: 'The data layer must not know about presentation.\n'
+              '${_render(offenders)}');
+    });
+
+    test('data imports no Flutter widget libraries', () {
+      // flutter/services is allowed: MethodChannel lives there, and that is
+      // the whole reason this layer is Flutter-aware at all.
+      const allowed = {'package:flutter/services.dart'};
+      final offenders = _importsMatching(
+        'lib/data',
+        (import) =>
+            import.startsWith('package:flutter/') && !allowed.contains(import),
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'The data layer may import package:flutter/services.dart only. '
+            'Anything else drags presentation into the transport.\n'
+            '${_render(offenders)}',
+      );
+    });
+
+    test('ui does not depend on a concrete data implementation', () {
+      // The UI talks to Iperf3Runner. main.dart is the composition root and is
+      // the one file allowed to name an implementation.
+      final offenders = _importsMatching(
+        'lib/ui',
+        (import) => import.contains('/data/'),
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'Presentation must depend on domain/services/iperf3_runner.dart '
+            'rather than on a transport. Only main.dart may pick an '
+            'implementation.\n${_render(offenders)}',
+      );
+    });
+
+    test('the headless entry point does not depend on ui', () {
+      // main_headless.dart is the standing proof that the core runs without a
+      // widget tree; an import from lib/ui would quietly end that.
+      final offenders = _importsMatching(
+        'lib',
+        (import) => import.contains('/ui/'),
+        onlyFiles: {'lib/main_headless.dart'},
+      );
+      expect(
+        offenders,
+        isEmpty,
+        reason: 'The headless entry point must run the core with no UI.\n'
+            '${_render(offenders)}',
+      );
+    });
+
+    test('every layer directory is actually covered by these rules', () {
+      // Guards against a new top-level layer appearing and silently escaping
+      // every rule above.
+      final layers = Directory('lib')
+          .listSync()
+          .whereType<Directory>()
+          .map((d) => d.path.split(Platform.pathSeparator).last)
+          .toSet();
+      expect(
+        layers,
+        equals({'domain', 'data', 'ui'}),
+        reason: 'A new layer appeared under lib/. Add rules for it here.',
+      );
+    });
+  });
+}
+
+/// Every `(file, import)` pair under [directory] whose import satisfies [test].
+List<({String file, String import})> _importsMatching(
+  String directory,
+  bool Function(String import) test, {
+  Set<String>? onlyFiles,
+}) {
+  final results = <({String file, String import})>[];
+  final dir = Directory(directory);
+  if (!dir.existsSync()) return results;
+
+  final pattern = RegExp(r'''^\s*import\s+['"]([^'"]+)['"]''', multiLine: true);
+  for (final entity in dir.listSync(recursive: true)) {
+    if (entity is! File || !entity.path.endsWith('.dart')) continue;
+    if (onlyFiles != null && !onlyFiles.contains(entity.path)) continue;
+    final source = entity.readAsStringSync();
+    for (final match in pattern.allMatches(source)) {
+      final import = match.group(1)!;
+      if (test(import)) {
+        results.add((file: entity.path, import: import));
+      }
+    }
+  }
+  return results;
+}
+
+String _render(List<({String file, String import})> offenders) =>
+    offenders.map((o) => '  ${o.file} → ${o.import}').join('\n');

test/domain/models/iperf3_event_test.dart

@@ -0,0 +1,107 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+
+void main() {
+  group('Iperf3Event.parse', () {
+    test('parses a start event', () {
+      const line = '{"event":"start","data":{'
+          '"connecting_to":{"host":"192.168.2.182","port":5201},'
+          '"test_start":{"protocol":"TCP","num_streams":4,"duration":10}}}';
+      final event = Iperf3Event.parse(line);
+      expect(event, isA<Iperf3Start>());
+      final start = event as Iperf3Start;
+      expect(start.targetHost, equals('192.168.2.182'));
+      expect(start.targetPort, equals(5201));
+      expect(start.streamCount, equals(4));
+      expect(start.durationSeconds, equals(10));
+      expect(start.protocol, equals('TCP'));
+    });
+
+    test('parses an interval event with per-stream detail', () {
+      const line = '{"event":"interval","data":{'
+          '"streams":[{"socket":143,"bytes":49283072,'
+          '"bits_per_second":394264576.0,"retransmits":0,"snd_cwnd":2023424,'
+          '"rtt":3521}],'
+          '"sum":{"start":0.0,"end":1.000151,"seconds":1.000151,'
+          '"bytes":98566144,"bits_per_second":788410352.0,"retransmits":0,'
+          '"omitted":false,"sender":true}}}';
+      final event = Iperf3Event.parse(line);
+      expect(event, isA<Iperf3Interval>());
+      final interval = event as Iperf3Interval;
+      expect(interval.bytes, equals(98566144));
+      expect(interval.bitsPerSecond, closeTo(788410352.0, 0.1));
+      expect(interval.retransmits, equals(0));
+      expect(interval.omitted, isFalse);
+      expect(interval.streams, hasLength(1));
+      expect(interval.streams.single.socket, equals(143));
+      expect(interval.streams.single.rtt, equals(3521));
+    });
+
+    test('marks omitted intervals', () {
+      const line = '{"event":"interval","data":{"streams":[],'
+          '"sum":{"start":0.0,"end":1.0,"bytes":1,"bits_per_second":8.0,'
+          '"omitted":true}}}';
+      final interval = Iperf3Event.parse(line) as Iperf3Interval;
+      expect(interval.omitted, isTrue);
+    });
+
+    test('parses an end event with sent and received totals', () {
+      const line = '{"event":"end","data":{'
+          '"sum_sent":{"seconds":10.0,"bytes":987654321,'
+          '"bits_per_second":790123456.0,"retransmits":7},'
+          '"sum_received":{"seconds":10.01,"bytes":987000000,'
+          '"bits_per_second":789000000.0},'
+          '"cpu_utilization_percent":{"host_total":12.5,"remote_total":3.25}}}';
+      final end = Iperf3Event.parse(line) as Iperf3End;
+      expect(end.sent!.bytes, equals(987654321));
+      expect(end.sent!.retransmits, equals(7));
+      expect(end.received!.bitsPerSecond, closeTo(789000000.0, 0.1));
+      expect(end.hostCpuPercent, closeTo(12.5, 0.01));
+      expect(end.remoteCpuPercent, closeTo(3.25, 0.01));
+    });
+
+    test('falls back to bidir-reverse keys when present', () {
+      const line = '{"event":"interval","data":{"streams":[],'
+          '"sum_bidir_reverse":{"start":0.0,"end":1.0,"bytes":42,'
+          '"bits_per_second":336.0}}}';
+      final interval = Iperf3Event.parse(line) as Iperf3Interval;
+      expect(interval.bytes, equals(42));
+    });
+
+    test('parses an error event', () {
+      const line = '{"event":"error","data":"unable to connect to server"}';
+      final event = Iperf3Event.parse(line);
+      expect(event, isA<Iperf3Error>());
+      expect((event as Iperf3Error).message,
+          equals('unable to connect to server'));
+    });
+
+    test('parses the bridge stop marker', () {
+      final event = Iperf3Event.parse('{"event":"jni_stopped","data":{}}');
+      expect(event, isA<Iperf3Stopped>());
+    });
+
+    test('surfaces non-JSON output as a log line rather than dropping it', () {
+      final event = Iperf3Event.parse('iperf3: something unexpected');
+      expect(event, isA<Iperf3LogLine>());
+      expect((event as Iperf3LogLine).text,
+          equals('iperf3: something unexpected'));
+    });
+
+    test('surfaces malformed JSON as a log line', () {
+      final event = Iperf3Event.parse('{"event":"interval",');
+      expect(event, isA<Iperf3LogLine>());
+    });
+
+    test('treats an unknown event name as a log line', () {
+      final event = Iperf3Event.parse('{"event":"future_thing","data":{}}');
+      expect(event, isA<Iperf3LogLine>());
+    });
+
+    test('tolerates a missing data object', () {
+      final event = Iperf3Event.parse('{"event":"interval"}');
+      expect(event, isA<Iperf3Interval>());
+      expect((event as Iperf3Interval).bytes, equals(0));
+    });
+  });
+}

test/domain/models/iperf3_session_test.dart

@@ -0,0 +1,135 @@
+// Pure-Dart tests for the run aggregate. No widgets, no bindings, no channel —
+// this is the part that has to be correct regardless of what draws it.
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_session.dart';
+
+void main() {
+  Iperf3Interval sample(double start, double bits,
+          {int bytes = 1000, int? retransmits, bool omitted = false}) =>
+      Iperf3Interval(
+        start: start,
+        end: start + 1,
+        bytes: bytes,
+        bitsPerSecond: bits,
+        retransmits: retransmits,
+        omitted: omitted,
+      );
+
+  group('Iperf3Session', () {
+    test('starts empty', () {
+      final session = Iperf3Session();
+      expect(session.isEmpty, isTrue);
+      expect(session.sampleCount, isZero);
+      expect(session.intervals, isEmpty);
+      expect(session.start, isNull);
+      expect(session.summary, isNull);
+      expect(session.errors, isEmpty);
+      expect(session.stopped, isFalse);
+      expect(session.hasError, isFalse);
+    });
+
+    test('statistics are null before any sample', () {
+      final session = Iperf3Session();
+      expect(session.latestBitsPerSecond, isNull);
+      expect(session.meanBitsPerSecond, isNull);
+      expect(session.peakBitsPerSecond, isNull);
+      expect(session.totalRetransmits, isNull);
+    });
+
+    test('records start, intervals and summary', () {
+      final session = Iperf3Session()
+        ..add(const Iperf3Start(targetHost: 'host', targetPort: 5201))
+        ..add(sample(0, 100))
+        ..add(const Iperf3End(
+          sent: Iperf3Total(seconds: 1, bytes: 10, bitsPerSecond: 80),
+        ));
+      expect(session.isEmpty, isFalse);
+      expect(session.start!.targetHost, equals('host'));
+      expect(session.sampleCount, equals(1));
+      expect(session.summary!.sent!.bitsPerSecond, equals(80));
+    });
+
+    test('excludes omitted warm-up intervals from the series', () {
+      final session = Iperf3Session()
+        ..add(sample(0, 10, omitted: true))
+        ..add(sample(1, 100))
+        ..add(sample(2, 200));
+      expect(session.sampleCount, equals(2));
+      expect(session.meanBitsPerSecond, equals(150),
+          reason: 'the omitted 10 would have pulled the mean to ~103');
+    });
+
+    test('computes mean, peak and latest over the samples', () {
+      final session = Iperf3Session()
+        ..add(sample(0, 100))
+        ..add(sample(1, 400))
+        ..add(sample(2, 250));
+      expect(session.latestBitsPerSecond, equals(250));
+      expect(session.peakBitsPerSecond, equals(400));
+      expect(session.meanBitsPerSecond, equals(250));
+    });
+
+    test('sums sampled bytes', () {
+      final session = Iperf3Session()
+        ..add(sample(0, 1, bytes: 1500))
+        ..add(sample(1, 1, bytes: 2500));
+      expect(session.sampledBytes, equals(4000));
+    });
+
+    test('sums retransmits when reported', () {
+      final session = Iperf3Session()
+        ..add(sample(0, 1, retransmits: 2))
+        ..add(sample(1, 1, retransmits: 5));
+      expect(session.totalRetransmits, equals(7));
+    });
+
+    test('retransmits stay null when never reported, not zero', () {
+      // UDP reports no retransmit counts; "not measured" must not read as 0.
+      final session = Iperf3Session()
+        ..add(sample(0, 1))
+        ..add(sample(1, 1));
+      expect(session.totalRetransmits, isNull);
+    });
+
+    test('collects errors in order and flags them', () {
+      final session = Iperf3Session()
+        ..add(const Iperf3Error('first'))
+        ..add(const Iperf3Error('second'));
+      expect(session.hasError, isTrue);
+      expect(session.errors, equals(['first', 'second']));
+      expect(session.isEmpty, isFalse);
+    });
+
+    test('records a stop', () {
+      final session = Iperf3Session()..add(const Iperf3Stopped());
+      expect(session.stopped, isTrue);
+    });
+
+    test('ignores log lines', () {
+      final session = Iperf3Session()..add(const Iperf3LogLine('noise'));
+      expect(session.isEmpty, isTrue);
+    });
+
+    test('clear returns it to the empty state', () {
+      final session = Iperf3Session()
+        ..add(const Iperf3Start(targetHost: 'host'))
+        ..add(sample(0, 100))
+        ..add(const Iperf3Error('boom'))
+        ..add(const Iperf3Stopped())
+        ..add(const Iperf3End())
+        ..clear();
+      expect(session.isEmpty, isTrue);
+      expect(session.stopped, isFalse);
+      expect(session.hasError, isFalse);
+      expect(session.peakBitsPerSecond, isNull);
+    });
+
+    test('exposed collections are unmodifiable', () {
+      final session = Iperf3Session()..add(sample(0, 1));
+      expect(() => session.intervals.add(sample(1, 1)), throwsUnsupportedError);
+      expect(() => session.errors.add('x'), throwsUnsupportedError);
+    });
+  });
+}

test/support/fake_iperf3_runner.dart

@@ -0,0 +1,62 @@
+import 'dart:async';
+
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_result.dart';
+import 'package:iperf3gui/domain/models/test_configuration.dart';
+import 'package:iperf3gui/domain/services/iperf3_runner.dart';
+
+/// In-memory [Iperf3Runner] for tests.
+///
+/// Implements the interface rather than the concrete service, so it tracks the
+/// five members the UI actually depends on instead of every public member the
+/// MethodChannel implementation happens to have.
+class FakeIperf3Runner implements Iperf3Runner {
+  FakeIperf3Runner({this.onRun});
+
+  /// Supplies the result for each [run], and may [emit] events first.
+  Future<Iperf3Result> Function(TestConfiguration)? onRun;
+
+  final StreamController<Iperf3Event> _controller =
+      StreamController<Iperf3Event>.broadcast();
+
+  /// Configurations passed to [run], in order.
+  final List<TestConfiguration> runCalls = [];
+
+  int stopCallCount = 0;
+  bool disposed = false;
+  bool _isRunning = false;
+
+  int get runCallCount => runCalls.length;
+
+  /// Push an event as if the native layer had reported it.
+  void emit(Iperf3Event event) => _controller.add(event);
+
+  @override
+  Stream<Iperf3Event> get events => _controller.stream;
+
+  @override
+  bool get isRunning => _isRunning;
+
+  @override
+  Future<Iperf3Result> run(TestConfiguration config) async {
+    runCalls.add(config);
+    _isRunning = true;
+    try {
+      if (onRun != null) return await onRun!(config);
+      return const Iperf3Result(rawOutput: '', exitCode: 0);
+    } finally {
+      _isRunning = false;
+    }
+  }
+
+  @override
+  Future<void> stop() async {
+    stopCallCount++;
+  }
+
+  @override
+  Future<void> dispose() async {
+    disposed = true;
+    await _controller.close();
+  }
+}

test/ui/features/test_run/iperf3_event_formatter_test.dart

@@ -0,0 +1,87 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/ui/features/test_run/iperf3_event_formatter.dart';
+
+void main() {
+  group('formatBytes', () {
+    test('scales in binary units the way iperf3 prints totals', () {
+      expect(formatBytes(0), equals('0.00 Bytes'));
+      expect(formatBytes(1024), equals('1.00 KBytes'));
+      expect(formatBytes(98566144), equals('94.0 MBytes'));
+      expect(formatBytes(1073741824), equals('1.00 GBytes'));
+    });
+  });
+
+  group('formatBitrate', () {
+    test('scales in decimal units, as network rates are quoted', () {
+      expect(formatBitrate(0), equals('0.00 bits/sec'));
+      expect(formatBitrate(8000), equals('8.00 Kbits/sec'));
+      expect(formatBitrate(790000000), equals('790 Mbits/sec'));
+      expect(formatBitrate(2500000000), equals('2.50 Gbits/sec'));
+    });
+  });
+
+  group('formatIperf3Event', () {
+    test('renders a start event', () {
+      const event = Iperf3Start(
+        targetHost: '192.168.2.182',
+        targetPort: 5201,
+        protocol: 'TCP',
+        streamCount: 1,
+        durationSeconds: 10,
+      );
+      final text = formatIperf3Event(event)!;
+      expect(text, contains('Connecting to host 192.168.2.182, port 5201'));
+      expect(text, contains('TCP'));
+      expect(text, contains('1 stream'));
+    });
+
+    test('renders an interval with retransmits', () {
+      const event = Iperf3Interval(
+        start: 0,
+        end: 1,
+        bytes: 98566144,
+        bitsPerSecond: 788410352,
+        retransmits: 3,
+      );
+      final text = formatIperf3Event(event)!;
+      expect(text, contains('0.00-1.00 sec'));
+      expect(text, contains('94.0 MBytes'));
+      expect(text, contains('788 Mbits/sec'));
+      expect(text, contains('3 retr'));
+    });
+
+    test('marks an omitted interval', () {
+      const event = Iperf3Interval(
+          start: 0, end: 1, bytes: 1, bitsPerSecond: 8, omitted: true);
+      expect(formatIperf3Event(event), contains('omitted'));
+    });
+
+    test('renders sender and receiver lines from an end event', () {
+      const event = Iperf3End(
+        sent: Iperf3Total(
+            seconds: 10, bytes: 987654321, bitsPerSecond: 790000000,
+            retransmits: 7),
+        received: Iperf3Total(
+            seconds: 10.01, bytes: 987000000, bitsPerSecond: 789000000),
+        hostCpuPercent: 12.5,
+      );
+      final text = formatIperf3Event(event)!;
+      expect(text, contains('sender'));
+      expect(text, contains('receiver'));
+      expect(text, contains('7 retr'));
+      expect(text, contains('CPU: local 12.5%'));
+    });
+
+    test('renders errors and stops', () {
+      expect(formatIperf3Event(const Iperf3Error('boom')),
+          equals('iperf3 error: boom'));
+      expect(formatIperf3Event(const Iperf3Stopped()),
+          equals('Stopped by user.'));
+    });
+
+    test('drops an empty log line', () {
+      expect(formatIperf3Event(const Iperf3LogLine('')), isNull);
+    });
+  });
+}

test/ui/features/test_run/test_run_view_model_test.dart

@@ -1,15 +1,17 @@
 import 'dart:async';
 
 import 'package:flutter_test/flutter_test.dart';
-import 'package:iperf3gui/data/services/iperf3_service.dart';
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
 import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/domain/models/test_configuration.dart';
 import 'package:iperf3gui/ui/features/test_run/test_run_view_model.dart';
 
+import '../../../support/fake_iperf3_runner.dart';
+
 void main() {
   group('TestRunViewModel', () {
     test('starts in idle state', () {
-      final vm = TestRunViewModel(iperf3Service: _MockIperf3Service());
+      final vm = TestRunViewModel(iperf3Service: FakeIperf3Runner());
       expect(vm.state, equals(TestRunState.idle));
       expect(vm.result, isNull);
       expect(vm.currentConfig, isNull);
@@ -17,13 +19,13 @@ void main() {
     });
 
     test('can be reset', () {
-      final vm = TestRunViewModel(iperf3Service: _MockIperf3Service());
+      final vm = TestRunViewModel(iperf3Service: FakeIperf3Runner());
       vm.reset();
       expect(vm.state, equals(TestRunState.idle));
     });
 
     test('invalid config sets error state without running', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       final vm = TestRunViewModel(iperf3Service: mock);
       const config = TestConfiguration(server: '');
       await vm.runTest(config);
@@ -32,7 +34,7 @@ void main() {
     });
 
     test('runTest with valid config calls service', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (config) async {
           expect(config.server, equals('192.168.1.1'));
           return const Iperf3Result(rawOutput: 'done', exitCode: 0);
@@ -46,7 +48,7 @@ void main() {
     });
 
     test('non-zero exit code lands in error state', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async =>
             const Iperf3Result(rawOutput: 'boom', exitCode: 1),
       );
@@ -56,11 +58,16 @@ void main() {
       expect(vm.result!.exitCode, equals(1));
     });
 
-    test('streamed lines accumulate into output during the run', () async {
+    test('streamed events accumulate into output during the run', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       mock.onRun = (_) async {
-        mock.emit('Connecting to host 192.168.1.1\n');
+        mock.emit(const Iperf3Start(targetHost: '192.168.1.1', targetPort: 5201));
-        mock.emit('[  5]   0.00-1.00   sec  11.2 MBytes  94.1 Mbits/sec\n');
+        mock.emit(const Iperf3Interval(
+          start: 0,
+          end: 1,
+          bytes: 11744051,
+          bitsPerSecond: 94100000,
+        ));
         // Let the broadcast stream deliver before the run resolves.
         await Future<void>.delayed(Duration.zero);
         return const Iperf3Result(rawOutput: 'ignored', exitCode: 0);
@@ -69,14 +76,51 @@ void main() {
       final vm = TestRunViewModel(iperf3Service: mock);
       await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
 
-      expect(vm.output, contains('Connecting to host'));
+      expect(vm.output, contains('Connecting to host 192.168.1.1'));
       expect(vm.output, contains('94.1 Mbits/sec'));
       // The streamed transcript wins over the service's own copy.
       expect(vm.output, isNot(contains('ignored')));
     });
 
+    test('events are fed into the session', () async {
+      final mock = FakeIperf3Runner();
+      mock.onRun = (_) async {
+        mock.emit(const Iperf3Interval(
+            start: 0, end: 1, bytes: 1000, bitsPerSecond: 8000));
+        mock.emit(const Iperf3End(
+          sent: Iperf3Total(seconds: 1, bytes: 1000, bitsPerSecond: 8000),
+        ));
+        await Future<void>.delayed(Duration.zero);
+        return const Iperf3Result(rawOutput: '', exitCode: 0);
+      };
+
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+
+      expect(vm.session.sampleCount, equals(1));
+      expect(vm.session.summary, isNotNull);
+    });
+
+    test('a new run clears the previous session', () async {
+      final mock = FakeIperf3Runner();
+      mock.onRun = (_) async {
+        mock.emit(const Iperf3Interval(
+            start: 0, end: 1, bytes: 1000, bitsPerSecond: 8000));
+        await Future<void>.delayed(Duration.zero);
+        return const Iperf3Result(rawOutput: '', exitCode: 0);
+      };
+
+      final vm = TestRunViewModel(iperf3Service: mock);
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.session.sampleCount, equals(1));
+
+      await vm.runTest(const TestConfiguration(server: '192.168.1.1'));
+      expect(vm.session.sampleCount, equals(1),
+          reason: 'not appended to the old run');
+    });
+
     test('falls back to result output when nothing streamed', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async =>
             const Iperf3Result(rawOutput: 'summary only', exitCode: 0),
       );
@@ -86,7 +130,7 @@ void main() {
     });
 
     test('output is cleared when a new run starts', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async =>
             const Iperf3Result(rawOutput: 'first', exitCode: 0),
       );
@@ -102,7 +146,7 @@ void main() {
     });
 
     test('stopTest forwards to the service only while running', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       final vm = TestRunViewModel(iperf3Service: mock);
 
       await vm.stopTest();
@@ -121,7 +165,7 @@ void main() {
     });
 
     test('wasStopped reflects a user-requested stop', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async => const Iperf3Result(
           rawOutput: 'stopped early',
           exitCode: 0,
@@ -136,7 +180,7 @@ void main() {
     });
 
     test('wasStopped is false for a run that finished on its own', () async {
-      final mock = _MockIperf3Service(
+      final mock = FakeIperf3Runner(
         onRun: (_) async =>
             const Iperf3Result(rawOutput: 'done', exitCode: 0),
       );
@@ -146,7 +190,7 @@ void main() {
     });
 
     test('a second runTest while running is ignored', () async {
-      final mock = _MockIperf3Service();
+      final mock = FakeIperf3Runner();
       final gate = Completer<Iperf3Result>();
       mock.onRun = (_) => gate.future;
 
@@ -160,49 +204,3 @@ void main() {
     });
   });
 }
-
-class _MockIperf3Service implements Iperf3Service {
-  _MockIperf3Service({this.onRun});
-
-  Future<Iperf3Result> Function(TestConfiguration)? onRun;
-
-  final StreamController<String> _controller =
-      StreamController<String>.broadcast();
-
-  int runCallCount = 0;
-  int stopCallCount = 0;
-  bool disposed = false;
-  bool _isRunning = false;
-
-  /// Push a line as if the native layer had emitted it.
-  void emit(String line) => _controller.add(line);
-
-  @override
-  Stream<String> get outputLines => _controller.stream;
-
-  @override
-  bool get isRunning => _isRunning;
-
-  @override
-  Future<Iperf3Result> run(TestConfiguration config) async {
-    runCallCount++;
-    _isRunning = true;
-    try {
-      if (onRun != null) return await onRun!(config);
-      return const Iperf3Result(rawOutput: '', exitCode: 0);
-    } finally {
-      _isRunning = false;
-    }
-  }
-
-  @override
-  Future<void> stop() async {
-    stopCallCount++;
-  }
-
-  @override
-  Future<void> dispose() async {
-    disposed = true;
-    await _controller.close();
-  }
-}

test/widget_test.dart

@@ -1,17 +1,89 @@
-// This is a basic Flutter widget test.
+// Widget-level smoke tests.
 //
-// To perform an interaction with a widget in your test, use the WidgetTester
+// These drive the real UI against a FakeIperf3Runner: no MethodChannel, no
-// utility in the flutter_test package. For example, you can send tap and scroll
+// native library, no device. That is only possible because the presentation
-// gestures. You can also use WidgetTester to find child widgets in the widget
+// layer depends on the Iperf3Runner interface rather than on Iperf3Service.
-// tree, read text, and verify that the values of widget properties are correct.
 
+import 'dart:async';
+
+import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import 'package:iperf3gui/domain/models/iperf3_event.dart';
+import 'package:iperf3gui/domain/models/iperf3_result.dart';
 import 'package:iperf3gui/main.dart';
 
+import 'support/fake_iperf3_runner.dart';
+
 void main() {
   testWidgets('App smoke test', (WidgetTester tester) async {
-    await tester.pumpWidget(const Iperf3GuiApp());
+    await tester.pumpWidget(Iperf3GuiApp(runner: FakeIperf3Runner()));
     expect(find.text('iperf3-gui'), findsOneWidget);
+    expect(find.text('GO'), findsOneWidget);
+    expect(find.text('Ready'), findsOneWidget);
+  });
+
+  testWidgets('runs a test and renders streamed results', (tester) async {
+    final runner = FakeIperf3Runner();
+    runner.onRun = (config) async {
+      runner.emit(Iperf3Start(
+        targetHost: config.server,
+        targetPort: config.port,
+        protocol: 'TCP',
+        streamCount: config.parallelStreams,
+      ));
+      runner.emit(const Iperf3Interval(
+        start: 0,
+        end: 1,
+        bytes: 98566144,
+        bitsPerSecond: 788410352,
+      ));
+      await Future<void>.delayed(Duration.zero);
+      return const Iperf3Result(rawOutput: '', exitCode: 0);
+    };
+
+    await tester.pumpWidget(Iperf3GuiApp(runner: runner));
+    await tester.tap(find.text('GO'));
+    await tester.pumpAndSettle();
+
+    expect(runner.runCallCount, equals(1));
+    expect(find.text('Test complete'), findsOneWidget);
+    expect(find.textContaining('788 Mbits/sec'), findsWidgets);
+    // The stat row is driven by the parsed interval series.
+    expect(find.text('peak'), findsOneWidget);
+  });
+
+  testWidgets('shows a stop button while running and can stop', (tester) async {
+    final runner = FakeIperf3Runner();
+    final gate = Completer<Iperf3Result>();
+    runner.onRun = (_) => gate.future;
+
+    await tester.pumpWidget(Iperf3GuiApp(runner: runner));
+    await tester.tap(find.text('GO'));
+    await tester.pump();
+
+    expect(find.text('STOP'), findsOneWidget);
+    expect(find.text('Running…'), findsOneWidget);
+
+    await tester.tap(find.text('STOP'));
+    await tester.pump();
+    expect(runner.stopCallCount, equals(1));
+
+    gate.complete(const Iperf3Result(
+        rawOutput: '', exitCode: 0, stopped: true));
+    await tester.pumpAndSettle();
+    expect(find.text('Stopped'), findsOneWidget);
+  });
+
+  testWidgets('rejects an empty server address', (tester) async {
+    final runner = FakeIperf3Runner();
+    await tester.pumpWidget(Iperf3GuiApp(runner: runner));
+
+    await tester.enterText(find.byType(TextField).first, '');
+    await tester.tap(find.text('GO'));
+    await tester.pumpAndSettle();
+
+    expect(runner.runCallCount, equals(0));
+    expect(find.textContaining('Invalid configuration'), findsOneWidget);
   });
 }