Fixing a bug that caused BackgroundThreadPosterTestDouble to hang whe…

…n multiple runnables with interdependencies and nested calls to BackgroundThreadPosterTestDouble were involved.

threadposter/src/main/java/com/techyourchance/threadposter/testdoubles/BackgroundThreadPosterTestDouble.java

@@ -29,9 +29,10 @@
     @Override
     public void post(Runnable runnable) {
         synchronized (MONITOR) {
+            mRunnables.add(runnable);
             mNonCompletedRunnables++;
+            MONITOR.notifyAll();
         }
-        mRunnables.add(runnable);
     }
 
     @Override
@@ -61,12 +62,11 @@ public void run() {
     }
 
     /**
-     * Call to this method will block until all {@link Runnable}s sent for execution by this
-     * "test double" BEFORE THE MOMENT OF A CALL will be completed.<br>
-     * Call to this method allows to establish a happens-before relationship between the
-     * {@link Runnable}s sent for execution and any subsequent code.
+     * Execute all {@link Runnable}s posted to this "test double". The caller will block until the operation completes<br>
+     * Call to this method allows to establish a happens-before relationship between the previously
+     * posted {@link Runnable}s and subsequent code.
      */
-    public void join() {
+    /* pp */ void join() {
         synchronized (MONITOR) {
             Runnable runnable;
             while (mNonCompletedRunnables > 0) {

threadposter/src/main/java/com/techyourchance/threadposter/testdoubles/UiThreadPosterTestDouble.java

@@ -36,7 +36,7 @@ public void post(final Runnable runnable) {
      * Call to this method allows to establish a happens-before relationship between the previously
      * posted {@link Runnable}s and subsequent code.
      */
-    public void join() {
+    /* pp */ void join() {
         final Thread fakeUiThread = new Thread() {
             @Override
             public void run() {

threadposter/src/test/java/com/techyourchance/threadposter/testdoubles/BackgroundThreadPosterTestDoubleTest.java

@@ -162,6 +162,40 @@ public void run() {
         assertThat(counter.getCount(), is(2));
     }
 
+    @Test
+    public void executeThenJoin_multipleNestedRunnablesInterdependent_sideEffectsVisibleAfterJoin() throws Exception {
+        // Arrange
+        final Counter counter = new Counter();
+        final Semaphore semaphore = new Semaphore(0);
+        final Runnable runnable1 = new Runnable() {
+            @Override
+            public void run() {
+                semaphore.release();
+                counter.increment();
+            }
+        };
+        final Runnable runnable2 = new Runnable() {
+            @Override
+            public void run() {
+                SUT.post(runnable1);
+                semaphore.acquireUninterruptibly();
+                counter.increment();
+            }
+        };
+        final Runnable runnable3 = new Runnable() {
+            @Override
+            public void run() {
+                SUT.post(runnable2);
+                counter.increment();
+            }
+        };
+        // Act
+        SUT.post(runnable3);
+        // Assert
+        SUT.join();
+        assertThat(counter.getCount(), is(3));
+    }
+
     /**
      * This class will be used in order to check side effects in tests
      */