Fix ResultMatchers#hasFailureContaining (junit-team#1292)

ResultMatchers.hasFailureContaining() should not match when the given PrintableResult has no failures.

Author: alb-i986

src/main/java/org/junit/experimental/results/ResultMatchers.java

@@ -66,9 +66,9 @@ public void describeTo(Description description) {
      * contains {@code string}
      */
     public static Matcher<PrintableResult> hasFailureContaining(final String string) {
-        return new BaseMatcher<PrintableResult>() {
-            public boolean matches(Object item) {
-                return item.toString().contains(string);
+        return new TypeSafeMatcher<PrintableResult>() {
+            public boolean matchesSafely(PrintableResult item) {
+                return item.failureCount() > 0 && item.toString().contains(string);
             }
 
             public void describeTo(Description description) {

src/test/java/org/junit/tests/experimental/results/ResultMatchersTest.java

@@ -1,14 +1,21 @@
 package org.junit.tests.experimental.results;
 
-import static org.hamcrest.CoreMatchers.containsString;
-import static org.hamcrest.CoreMatchers.is;
-import static org.junit.Assert.assertThat;
-
 import org.junit.Test;
+import org.junit.experimental.results.PrintableResult;
 import org.junit.experimental.results.ResultMatchers;
 import org.junit.experimental.theories.Theory;
+import org.junit.runner.Description;
+import org.junit.runner.notification.Failure;
+
+import java.util.ArrayList;
+import java.util.Collections;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
 
 public class ResultMatchersTest {
+
     @Test
     public void hasFailuresHasGoodDescription() {
         assertThat(ResultMatchers.failureCountIs(3).toString(),
@@ -20,4 +27,20 @@ public void hasFailuresDescriptionReflectsInput(int i) {
         assertThat(ResultMatchers.failureCountIs(i).toString(),
                 containsString("" + i));
     }
+
+    @Test
+    public void hasFailureContaining_givenResultWithNoFailures() {
+        PrintableResult resultWithNoFailures = new PrintableResult(new ArrayList<Failure>());
+
+        assertThat(ResultMatchers.hasFailureContaining("").matches(resultWithNoFailures), is(false));
+    }
+
+    @Test
+    public void hasFailureContaining_givenResultWithOneFailure() {
+        PrintableResult resultWithOneFailure = new PrintableResult(Collections.singletonList(
+                new Failure(Description.EMPTY, new RuntimeException("my failure"))));
+
+        assertThat(ResultMatchers.hasFailureContaining("my failure").matches(resultWithOneFailure), is(true));
+        assertThat(ResultMatchers.hasFailureContaining("his failure").matches(resultWithOneFailure), is(false));
+    }
 }