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This module contains a number of utilities and helpers to help with testing. It is based on the junit 4 paradigms, but may be updated to work with junit 5 when that is out and stable. It consists of a number of mostly independent parts.

Concurrency and Time

In the concurrency and time group you have the FakeClock and two fake ExecutorService implementations. These are designed so that you can modify the clock as time goes on, and that will in turn trigger the executor to do scheduled tasks. E.g.:

class MyTest {
    private FakeClock clock;
    private FakeScheduledExecutor executor;

    public void setUp() {
        clock = new FakeClock();
        executor = new FakeScheduledExecutor(clock);

    public void testSomethingScheduled() {
        Something something = new Something();
        executor.schedule(something, 10, TimeUnit.SECONDS);

        assertThat(something.isComplete(), is(false));

        clock.tick(10, TimeUnit.SECONDS);

        assertThat(something.isComplete(), is(true));

There is also a simpler ImmediateExecutor that is a simple ExecutorService (not scheduled), and will run all tasks immediately. Note that this may cause problems if you have tasks that spawns new tasks all the time.

Terminal Input and Output

When having a program (or module) that prints to standard out, error or needs input from standard in, you need to emulate a real console or terminal. With the ConsoleWatcher you can easily emulate standard in input, and get whatever was written to standard out to be verified in the test. E.g.:

class MyTest {
    ConsoleWatcher console = new ConsoleWatcher().dumpOnFailure();

    public void testSomething() {
        console.setInput('a', '\n', Char.ESC);

        AtomicInteger exit = new AtomicInteger(0);
        MyProgram program = new MyProgram() {
            protected void exit(int i) {


        assertThat(console.getOutput(), is(""));
        assertThat(console.getError(), is("Invalid input: " + Strings.escape(Char.ESC)));
        assertThat(exit.get(), is(1));

Extra Matchers and Utils

There is also a set of extra matchers following the hamcrest matcher interface. All of these are static methods of the ExtraMatchers class.

  • equalIgnoreIndent: Same as isEqualIgnoreSpaces, but only ignores differences in spaces before the first printable character on each line. All other space chars must match.
  • equalToLines: Is essentially the same as a string-based equalTo, but will make a line by line diff-based output instead of the standard char-by-char output. If a rather large multi-line string is compared, it may simplify debugging quite a lot to get the right failure output.
  • allItemsMatch: Is a matcher that takes any collection, and compares every item in that collection with a given matcher.
  • oneOf: Is a matcher that checks that the given value is one of the expected values. This forwards to a hamcrest matcher.
  • distinctFrom: Is a matcher that takes any collection, compares it to another collection, and checks that there are no common items between the two.
  • inRange: checks that a number is in a specific numeric range. E.g. assertThat(sut.getNumSeals(), is(inRange(0, 10))) will check that ‘getNumSeals()’ returns a vlaue of [0..9] respectively (inRange follows the lower-inclusive, higher-exclusive range standard).
  • matchesRegex: Is a string matcher that checks if the string matches a specific regex. It uses the standard java Pattern syntax.

It is also common to have test resources that needs to be moved into temporary folders for a specific method to be able to be tested. The ResourceUtils class has a number of helper methods related to this.

Releasing Testing-Util

Run the maven versions plugin to see what has been updated of dependencies and plugins. See if updates should be done. Usually it’s better to depend on newer versions, as you may drag in older versions into other projects that misses features or has specific bugs.

mvn versions:display-dependency-updates
mvn versions:display-plugin-updates

Making the release cut.

# Do the maven release:
mvn release:prepare
mvn release:perform
mvn release:clean
git fetch origin

If the artifacts found at the Nexus Repository Manager are correct, you’re ready to make the release. If not a git hard rollback is needed (to remove release version, tag and commits). First make the actual binary release: