2.x: Clarify TestObserver.assertValueSet in docs and via tests

src/main/java/io/reactivex/observers/BaseTestConsumer.java

@@ -565,9 +565,14 @@ public final U assertValuesOnly(T... values) {
     }
 
     /**
-     * Assert that the TestObserver/TestSubscriber received only the specified values in any order.
-     * <p>This helps asserting when the order of the values is not guaranteed, i.e., when merging
+     * Assert that the TestObserver/TestSubscriber received only items that are in the specified
+     * collection as well irrespective of the order they were received.
+     * <p>
+     * This helps asserting when the order of the values is not guaranteed, i.e., when merging
      * asynchronous streams.
+     * <p>
+     * To ensure that only the expected items have been received, no more and no less, in any order,
+     * apply {@link #assertValueCount(int)} with {@code expected.size()}.
      *
      * @param expected the collection of values expected in any order
      * @return this

src/test/java/io/reactivex/observers/TestObserverTest.java

@@ -1626,4 +1626,38 @@ public void assertValueSequenceOnlyThrowsWhenErrored() {
             // expected
         }
     }
+
+    @Test
+    public void assertValueSetWiderSet() {
+        Set<Integer> set = new HashSet<Integer>(Arrays.asList(0, 1, 2, 3, 4, 5, 6, 7));
+
+        Observable.just(4, 5, 1, 3, 2)
+        .test()
+        .assertValueSet(set);
+    }
+
+    @Test
+    public void assertValueSetExact() {
+        Set<Integer> set = new HashSet<Integer>(Arrays.asList(1, 2, 3, 4, 5));
+
+        Observable.just(4, 5, 1, 3, 2)
+        .test()
+        .assertValueSet(set)
+        .assertValueCount(set.size());
+    }
+
+    @Test
+    public void assertValueSetMissing() {
+        Set<Integer> set = new HashSet<Integer>(Arrays.asList(0, 1, 2, 4, 5, 6, 7));
+
+        try {
+            Observable.range(1, 5)
+            .test()
+            .assertValueSet(set);
+
+            throw new RuntimeException("Should have failed");
+        } catch (AssertionError ex) {
+            assertTrue(ex.getMessage(), ex.getMessage().contains("Value not in the expected collection: " + 3));
+        }
+    }
 }

src/test/java/io/reactivex/subscribers/TestSubscriberTest.java

@@ -2186,4 +2186,38 @@ public void awaitCount0() {
         TestSubscriber<Integer> ts = TestSubscriber.create();
         ts.awaitCount(0, TestWaitStrategy.SLEEP_1MS, 0);
     }
+
+    @Test
+    public void assertValueSetWiderSet() {
+        Set<Integer> set = new HashSet<Integer>(Arrays.asList(0, 1, 2, 3, 4, 5, 6, 7));
+
+        Flowable.just(4, 5, 1, 3, 2)
+        .test()
+        .assertValueSet(set);
+    }
+
+    @Test
+    public void assertValueSetExact() {
+        Set<Integer> set = new HashSet<Integer>(Arrays.asList(1, 2, 3, 4, 5));
+
+        Flowable.just(4, 5, 1, 3, 2)
+        .test()
+        .assertValueSet(set)
+        .assertValueCount(set.size());
+    }
+
+    @Test
+    public void assertValueSetMissing() {
+        Set<Integer> set = new HashSet<Integer>(Arrays.asList(0, 1, 2, 4, 5, 6, 7));
+
+        try {
+            Flowable.range(1, 5)
+            .test()
+            .assertValueSet(set);
+
+            throw new RuntimeException("Should have failed");
+        } catch (AssertionError ex) {
+            assertTrue(ex.getMessage(), ex.getMessage().contains("Value not in the expected collection: " + 3));
+        }
+    }
 }