1.x: TestSubscriber/TestObserver print values if number of items doesn't match (#3880)

Author: artem-zinnatullin

src/main/java/rx/observers/TestObserver.java

@@ -113,7 +113,11 @@ public List<Object> getEvents() {
      */
     public void assertReceivedOnNext(List<T> items) {
         if (onNextEvents.size() != items.size()) {
-            throw new AssertionError("Number of items does not match. Provided: " + items.size() + "  Actual: " + onNextEvents.size());
+            throw new AssertionError("Number of items does not match. Provided: " + items.size() + "  Actual: " + onNextEvents.size()
+            + ".\n"
+            + "Provided values: " + items
+            + "\n"
+            + "Actual values: " + onNextEvents);
         }
 
         for (int i = 0; i < items.size(); i++) {

src/test/java/rx/observers/TestObserverTest.java

@@ -53,7 +53,9 @@ public void testAssertNotMatchCount() {
         oi.subscribe(o);
 
         thrown.expect(AssertionError.class);
-        thrown.expectMessage("Number of items does not match. Provided: 1  Actual: 2");
+        thrown.expectMessage("Number of items does not match. Provided: 1  Actual: 2.\n" +
+                "Provided values: [1]\n" +
+                "Actual values: [1, 2]");
 
         o.assertReceivedOnNext(Arrays.asList(1));
         assertEquals(2, o.getOnNextEvents().size());

src/test/java/rx/observers/TestSubscriberTest.java

@@ -595,4 +595,24 @@ public void onError(Throwable e) {
 
         ts.awaitTerminalEvent();
     }
+
+    @Test
+    public void assertValuesShouldThrowIfNumberOfItemsDoesNotMatch() {
+        TestSubscriber<String> ts = new TestSubscriber<String>();
+
+        ts.onNext("a");
+        ts.onNext("b");
+        ts.onNext("c");
+
+        try {
+            ts.assertValues("1", "2");
+            fail();
+        } catch (AssertionError expected) {
+            assertEquals("Number of items does not match. Provided: 2  Actual: 3.\n" +
+                    "Provided values: [1, 2]\n" +
+                    "Actual values: [a, b, c]",
+                    expected.getMessage()
+            );
+        }
+    }
 }