creating a new junit 5 project in gradle in intellij

I haven’t created a new JUnit 5/Gradle project in a IntelliJ in a long time. When doing so today, I ran into a number of problems. I wound up just starting over, but writing up what I encountered/learned.

Java 16 vs 17

IntelliJ supports Java 17. When I set up Gradle, it told me that Gradle doesn’t yet support Java 17. I confirmed on the Gradle website this is true. Ok that’s fair. Java 17 isn’t fully released for another month. While there might be an early adopter package that does work with Java 17, my focus here is JUnit 5, no, Java 17. So I went with Java 16.

String not found – “Package java.lang is declared in module java.base, which is not in the module graph”

This surprised me. I’m not using modules in this project. Or at least I don’t want to be, nor do I have a file. I tried invalidating the IntelliJ cache and restarting the IDE. That didn’t work. I then tried deleting the .gradle and .idea directories and reopening IntelliJ. That worked. IntellIJ even asked if I wanted to trust the gradle project as it recreated one.

This approach lost all IntelliJ settings including Java version, gradle version and source/test directories.

Recreating the project

At this point, I decided to delete my build.gradle and settings.gradle files in addition to the .idea and .gradle directories. My plan was to start over. I then created a new Gradle project in the same directory. I created a dummy file and had IntellIJ create a JUnit 5 test for me. That updated the Gradle file in a way that the IDEA was happy with. Now to commit to git lest anything else happen.

ant and junit 5 – outputting test duration and failure to the log

In JUnit 5, you use the junitlauncher Ant task rather than the junit Ant task.¬†Unfortunately, this isn’t a drop in replacement. In addition to needing a workaround to set system properties, you also need a workaround to write the test results to the console log.

JUnit 4

With JUnit 4 and Ant, you got output that looked list this for each test run. In the console. Real time while the build was running. This was really useful.

[junit] Running com.javaranch.jforum.MissingHeadTagTest
[junit] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 1.685 sec

The problem

JUnit 5 itself provides a number of built in options for this. However, Ant integration renders this “not very useful” for a few reasons.

    1. I want to use the legacy listeners. For example:
      <listener type="legacy-xml" sendSysOut="true" sendSysErr="true" />
      <listener type="legacy-plain"sendSysOut="true"sendSysErr="true"/>

      However, if I enabled sendSysOut and sendSysErr to them, all the listeners present redirect away from System.out. This means if I try to use the built it LoggingListener, it also redirects to the file and I don’t see it in the console. This means, I have to chose between the legacy listeners and seeing real time data.

    2. Ant seems to pass a fileset as individual tests. This means that running this code, prints a summary for each test rather than the whole thing at the end.
      <junitlauncher haltOnFailure="true" printsummary="true">
           <classpath refid="test.classpath" />
           <testclasses outputdir="build/test-report">
      	<fileset dir="build/test">
      	  <include name="**/*Tests.class" />

      It looks like this. The summary tells me about each run, but not with the test names so not useful anyway.

      [junitlauncher] Test run finished after 117 ms
      [junitlauncher] [         3 containers found      ]
      [junitlauncher] [         0 containers skipped    ]
      [junitlauncher] [         3 containers started    ]
      [junitlauncher] [         0 containers aborted    ]
      [junitlauncher] [         3 containers successful ]
      [junitlauncher] [         0 containers failed     ]
      [junitlauncher] [        15 tests found           ]
      [junitlauncher] [         0 tests skipped         ]
      [junitlauncher] [        15 tests started         ]
      [junitlauncher] [         0 tests aborted         ]
      [junitlauncher] [        15 tests successful      ]
      [junitlauncher] [         0 tests failed          ]
      [junitlauncher] Test run finished after 14 ms
      [junitlauncher] [         2 containers found      ]
      [junitlauncher] [         0 containers skipped    ]
      [junitlauncher] [         2 containers started    ]
      [junitlauncher] [         0 containers aborted    ]
      [junitlauncher] [         2 containers successful ]
      [junitlauncher] [         0 containers failed     ]
      [junitlauncher] [        10 tests found           ]
      [junitlauncher] [         0 tests skipped         ]
      [junitlauncher] [        10 tests started         ]
      [junitlauncher] [         0 tests aborted         ]
      [junitlauncher] [        10 tests successful      ]
      [junitlauncher] [         0 tests failed          ]
    3. If I use JUnit Launcher’s fail on error property, it fails on the first test rather than telling me about all of them. (I don’t use this feature anyway.)
    4. Custom extensions also have their system out/err redirected to the legacy listeners.

The solution

This feels like a hacky workaround. But I only have one project that uses Ant so I don’t have to worry about duplicate code. The legacy listeners are useful so I don’t want to get rid of them.

I wrote a custom listener that stores the results in memory for each test and writes it to disk after each test class runs. That way it gets all the data, not just the last one. And then Ant writes it out.

<target name="test.junit.launcher" depends="compile">
		<junitlauncher haltOnFailure="false" printsummary="false">
			<classpath refid="test.classpath" />
			<testclasses outputdir="build/test-report">
				<fileset dir="build/test">
					<include name="**/*Tests.class" />
				<listener type="legacy-xml" sendSysOut="true" sendSysErr="true" />
				<listener type="legacy-plain" sendSysOut="true" sendSysErr="true" />
				<listener classname="com.example.project.CodeRanchListener" />
		<loadfile property="summary" srcFile="build/status-as-tests-run.txt" />

And the listener

package com.example.project;

import java.time.*;

import org.junit.platform.engine.*;
import org.junit.platform.engine.TestDescriptor.*;
import org.junit.platform.engine.TestExecutionResult.*;
import org.junit.platform.launcher.*;

public class MyListener implements TestExecutionListener {
	private StringWriter inMemoryWriter = new StringWriter();

	private int numSkippedInCurrentClass;
	private int numAbortedInCurrentClass;
	private int numSucceededInCurrentClass;
	private int numFailedInCurrentClass;
	private Instant startCurrentClass;

	private void resetCountsForNewClass() {
		numSkippedInCurrentClass = 0;
		numAbortedInCurrentClass = 0;
		numSucceededInCurrentClass = 0;
		numFailedInCurrentClass = 0;
		startCurrentClass =;

	public void executionStarted(TestIdentifier testIdentifier) {
		if ("[engine:junit-jupiter]".equals(testIdentifier.getParentId().orElse(""))) {
			println("Ran " + testIdentifier.getLegacyReportingName());

	public void executionSkipped(TestIdentifier testIdentifier, String reason) {

	public void executionFinished(TestIdentifier testIdentifier, TestExecutionResult testExecutionResult) {
		if ("[engine:junit-jupiter]".equals(testIdentifier.getParentId().orElse(""))) {
			int totalTestsInClass = numSucceededInCurrentClass + numAbortedInCurrentClass
					+ numFailedInCurrentClass + numSkippedInCurrentClass;
			Duration duration = Duration.between(startCurrentClass,;
			double numSeconds = duration.getNano() / (double) 1_000_000_000;
			String output = String.format("Tests run: %d, Failures: %d, Aborted: %d, Skipped: %d, Time elapsed: %f sec",
					totalTestsInClass, numFailedInCurrentClass, numAbortedInCurrentClass,
					numSkippedInCurrentClass, numSeconds);

		// don't count containers since looking for legacy JUnit 4 counting style
		if (testIdentifier.getType() == Type.TEST) {
			if (testExecutionResult.getStatus() == Status.SUCCESSFUL) {
			} else if (testExecutionResult.getStatus() == Status.ABORTED) {
				println("  ABORTED: " + testIdentifier.getDisplayName());
			} else if (testExecutionResult.getStatus() == Status.FAILED) {
				println("  FAILED: " + testIdentifier.getDisplayName());
	private void println(String str) {
		inMemoryWriter.write(str + "\n");
	 * Append to file on disk since listener can't write to System.out (becuase legacy listeners enabled)
	private void flushToDisk() {
		try (FileWriter writer = new FileWriter("build/status-as-tests-run.txt", true)) {
		} catch (IOException e) {
			throw new UncheckedIOException(e);

	public void testPlanExecutionFinished(TestPlan testPlan) {


ant and junit5 – simulating sysproperty

In JUnit 5, you use the junitlauncher Ant task rather than the junit Ant task.¬†Unfortunately, this isn’t a drop in replacement. For example, junitlauncher doesn’t offer the option to fork and run the JUnit tests. As a result, it also doesn’t have the nested sysproperty tag so you can pass system properties. This is a problem.

For the CodeRanch, we set a system property for the default file encoding. Since developers are around the world, we can’t assume everyone “just has” the encoding set.


Since JUnit 5 functionality for Ant was introduced this year, I’m hoping what I did in this post is a short term workaround.

Option 1 – pass to Ant

You can pass the the properties to Ant itself as described on Stack Overflow. For example:



  • simple


  • subpar – all the developers need to remember to do this. The reason we had it in Ant in the first place is so folks wouldn’t need to remember
  • for some use cases, the desired system properties could be derived and not know when calling Ant

Option 2- Nashorn Code

Since JUnit 5 is being run in the same process as Ant itself, you need to set the system property in memory. Luckily, Ant allows you to run scripting in various languages. I chose Nashorn because it is built into Java. (There are other variants of this; see below)

<script language="javascript">
    var imports = new JavaImporter(java.lang.System);
    imports.System.setProperty('file.encoding', 'ISO8859_1')


  • Short and simple
  • Nashorn is deprecated for removal starting Java 11. This means at some point, it can be removed. (I’m hopeful that the Ant task itself will support system properties by then.


  • Requires Java 8 or higher
  • The System property is set for the remainder of the build (you could write another code block to null it out after the test if this is a problem)

Variants of option 2

If you are running Ant with a version of Java below Java 8, you could use¬†this technique, but use Rhino instead. I didn’t test this, but I think the code is

System.setProperty('file.encoding', 'ISO8859_1')

JUnit 5 itself uses Java 8 so nobody would be in the situation of pre-Java 8 and trying to use this blog post.

If you are running Ant with a version of Java where Nashorn has been removed, you could use Groovy or Jython as the embedded language. The code is simpler. I didn’t chose this because it requires adding another jar to the Ant directory. I prefer to minimize these set up extensions. Especially for a feature like this which is likely to be temporary.

System.setProperty('file.encoding', 'ISO8859_1')