Print Diffs (Markdown) only once when needed

Author: XJ114514

junit-platform-console/src/main/java/org/junit/platform/console/tasks/ConsoleTestExecutor.java

@@ -184,9 +184,13 @@ private void printSummary(TestExecutionSummary summary, PrintWriter out) {
 		// Otherwise the failures have already been printed in detail
 		if (EnumSet.of(Details.NONE, Details.SUMMARY, Details.TREE).contains(outputOptions.getDetails())) {
 			summary.printFailuresTo(out);
+			boolean[] diffFlag = {true};
 			//adding diff code here
-			out.printf("%nDiffs (Markdown):%n");
 			summary.getFailures().forEach(failure -> {
+				if(diffFlag[0]){
+					out.printf("%nDiffs (Markdown):%n");
+					diffFlag[0] = false;
+				}
 				//get AssertionFailedError
 				if (failure.getException() instanceof AssertionFailedError) {
 					AssertionFailedError assertionFailedError = (AssertionFailedError) failure.getException();
@@ -197,7 +201,6 @@ private void printSummary(TestExecutionSummary summary, PrintWriter out) {
 						new DiffPrinter(testPlanListeners).printDiff(out, expected.getStringRepresentation(),
 							actual.getStringRepresentation(), failure.getTestIdentifier());
 					}
-
 				}
 			});
 		}