Merge pull request junit-team#319 from stefanbirkner/issue318

Fixed junit-teamgh-318 (Empty message instead of null)

src/main/java/junit/framework/AssertionFailedError.java

@@ -11,6 +11,10 @@ public AssertionFailedError() {
 	}
 
 	public AssertionFailedError(String message) {
-		super(message);
+		super(defaultString(message));
+	}
+
+	private static String defaultString(String message) {
+		return message == null ? "" : message;
 	}
 }

src/test/java/junit/tests/framework/AllTests.java

@@ -18,6 +18,7 @@ public static Test suite() {
 		suite.addTestSuite(TestCaseTest.class);
 		suite.addTest(SuiteTest.suite()); // Tests suite building, so can't use automatic test extraction 
 		suite.addTestSuite(TestListenerTest.class);
+		suite.addTestSuite(AssertionFailedErrorTest.class);
 		suite.addTestSuite(AssertTest.class);
 		suite.addTestSuite(TestImplementorTest.class);
 		suite.addTestSuite(NoArgTestCaseTest.class);

src/test/java/junit/tests/framework/AssertionFailedErrorTest.java

@@ -0,0 +1,23 @@
+package junit.tests.framework;
+
+import junit.framework.AssertionFailedError;
+import junit.framework.TestCase;
+
+public class AssertionFailedErrorTest extends TestCase {
+	private static final String ARBITRARY_MESSAGE= "arbitrary message";
+
+	public void testCreateErrorWithoutMessage() throws Exception {
+		AssertionFailedError error= new AssertionFailedError();
+		assertNull(error.getMessage());
+	}
+
+	public void testCreateErrorWithMessage() throws Exception {
+		AssertionFailedError error= new AssertionFailedError(ARBITRARY_MESSAGE);
+		assertEquals(ARBITRARY_MESSAGE, error.getMessage());
+	}
+
+	public void testCreateErrorWithoutMessageInsteadOfNull() throws Exception {
+		AssertionFailedError error= new AssertionFailedError(null);
+		assertEquals("", error.getMessage());
+	}
+}