UnitTest confirming compilation failure without super/extends and success with them.

- only testing zip operator at this time

Author: benjchristensen

rxjava-core/src/test/java/rx/CovarianceTest.java

@@ -0,0 +1,99 @@
+package rx;
+
+import org.junit.Test;
+
+import rx.util.functions.Action1;
+import rx.util.functions.Func2;
+
+/**
+ * Test super/extends of generics.
+ * 
+ * See https://github.com/Netflix/RxJava/pull/331
+ */
+public class CovarianceTest {
+
+    /**
+     * This won't compile if super/extends isn't done correctly on generics
+     */
+    @Test
+    public void testCovarianceOfZip() {
+        Observable<HorrorMovie> horrors = Observable.from(new HorrorMovie());
+        Observable<CoolRating> ratings = Observable.from(new CoolRating());
+
+        Func2<Media, Rating, ExtendedResult> combine = new Func2<Media, Rating, ExtendedResult>() {
+            @Override
+            public ExtendedResult call(Media m, Rating r) {
+                return new ExtendedResult();
+            }
+        };
+
+        Observable.<Result, Movie, CoolRating> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<Result>() {
+
+            @Override
+            public void call(Result t1) {
+                System.out.println("Result: " + t1);
+            }
+
+        });
+
+        Observable.<Result, Movie, CoolRating> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<Result>() {
+
+            @Override
+            public void call(Result t1) {
+                System.out.println("Result: " + t1);
+            }
+
+        });
+
+        Observable.<ExtendedResult, Media, Rating> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<ExtendedResult>() {
+
+            @Override
+            public void call(ExtendedResult t1) {
+                System.out.println("Result: " + t1);
+            }
+
+        });
+
+        Observable.<Result, Media, Rating> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<Result>() {
+
+            @Override
+            public void call(Result t1) {
+                System.out.println("Result: " + t1);
+            }
+
+        });
+
+        Observable.<ExtendedResult, Media, Rating> zip(horrors, ratings, combine).toBlockingObservable().forEach(new Action1<Result>() {
+
+            @Override
+            public void call(Result t1) {
+                System.out.println("Result: " + t1);
+            }
+
+        });
+
+        Observable.<Result, Movie, CoolRating> zip(horrors, ratings, combine);
+
+    }
+
+    static class Media {
+    }
+
+    static class Movie extends Media {
+    }
+
+    static class HorrorMovie extends Movie {
+    }
+
+    static class Rating {
+    }
+
+    static class CoolRating extends Rating {
+    }
+
+    static class Result {
+    }
+
+    static class ExtendedResult extends Result {
+    }
+}