1.x: negative argument check for skip's count and merge's maxConcurrent

src/main/java/rx/internal/operators/OperatorMerge.java

@@ -81,6 +81,9 @@ public static <T> OperatorMerge<T> instance(boolean delayErrors) {
      * @return
      */
     public static <T> OperatorMerge<T> instance(boolean delayErrors, int maxConcurrent) {
+        if (maxConcurrent <= 0) {
+            throw new IllegalArgumentException("maxConcurrent > 0 required but it was " + maxConcurrent);
+        }
         if (maxConcurrent == Integer.MAX_VALUE) {
             return instance(delayErrors);
         }

src/main/java/rx/internal/operators/OperatorSkip.java

@@ -31,6 +31,9 @@ public final class OperatorSkip<T> implements Observable.Operator<T, T> {
     final int toSkip;
 
     public OperatorSkip(int n) {
+        if (n < 0) {
+            throw new IllegalArgumentException("n >= 0 required but it was " + n);
+        }
         this.toSkip = n;
     }
 

src/test/java/rx/internal/operators/OperatorMergeTest.java

@@ -1333,4 +1333,24 @@ public void testConcurrencyLimit() {
         ts.assertValue(0);
         ts.assertCompleted();
     }
+
+    @Test
+    public void negativeMaxConcurrent() {
+        try {
+            Observable.merge(Arrays.asList(Observable.just(1), Observable.just(2)), -1);
+            fail("Expected IllegalArgumentException");
+        } catch (IllegalArgumentException e) {
+            assertEquals("maxConcurrent > 0 required but it was -1", e.getMessage());
+        }
+    }
+
+    @Test
+    public void zeroMaxConcurrent() {
+        try {
+            Observable.merge(Arrays.asList(Observable.just(1), Observable.just(2)), 0);
+            fail("Expected IllegalArgumentException");
+        } catch (IllegalArgumentException e) {
+            assertEquals("maxConcurrent > 0 required but it was 0", e.getMessage());
+        }
+    }
 }

src/test/java/rx/internal/operators/OperatorSkipTest.java

@@ -16,6 +16,7 @@
 package rx.internal.operators;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
 import static org.mockito.Matchers.any;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
@@ -37,17 +38,12 @@ public class OperatorSkipTest {
 
     @Test
     public void testSkipNegativeElements() {
-
-        Observable<String> skip = Observable.just("one", "two", "three").lift(new OperatorSkip<String>(-99));
-
-        @SuppressWarnings("unchecked")
-        Observer<String> observer = mock(Observer.class);
-        skip.subscribe(observer);
-        verify(observer, times(1)).onNext("one");
-        verify(observer, times(1)).onNext("two");
-        verify(observer, times(1)).onNext("three");
-        verify(observer, never()).onError(any(Throwable.class));
-        verify(observer, times(1)).onCompleted();
+        try {
+            Observable.just("one", "two", "three").skip(-99);
+            fail("Expected IllegalArgumentException");
+        } catch (IllegalArgumentException e) {
+            assertEquals("n >= 0 required but it was -99", e.getMessage());
+        }
     }
 
     @Test