I have written my first ArchUnit test as normal unit test for one of my Maven modules. It should ensure, that there is a test class for each cleass in the production set of classes.

But I strugle to make it reuseable, so that I can use it in other (Maven) modules. In contrast to the examples in the documentation of ArchUnit, which uses @ArchTest, I have to deal with two set of classes.

Any idea?

@Test
void eachClassMustHaveACorrespondingTestClass() {
    String packageName = SystemSpec.class.getPackageName();
    String[] splitter = StringUtils.split(packageName, '.');
    String[] packages = ArrayUtils.subarray(splitter, 0, splitter.length - 1);
    String parentPackage = String.join(".", packages);

    JavaClasses productionClasses = new ClassFileImporter()
            .withImportOption(new ImportOption.DoNotIncludeTests())
            .importPackages(parentPackage)
            .that(new IsNotAnEnum())
            .that(new IsInterfaceWithDefaultMethods());

    Set<String> testClassNames = new ClassFileImporter()
            .withImportOption(ImportOption.Predefined.DO_NOT_INCLUDE_JARS)
            .withImportOption(ImportOption.Predefined.ONLY_INCLUDE_TESTS)
            .importPackages(parentPackage) // Paket der Testklassen
            .stream()
            .map(JavaClass::getSimpleName)
            .collect(Collectors.toSet());

    ArchCondition<JavaClass> haveCorrespondingTestClass = new ArchCondition<>("have corresponding test class") {
        @Override
        public void check(JavaClass item, ConditionEvents events) {
            String testClassName = item.getSimpleName() + "Test";
            if (!testClassNames.contains(testClassName)) {
                String message = String.format("No test class found for %s", item.getFullName());
                events.add(SimpleConditionEvent.violated(item, message));
            }
        }
    };

    classes().should(haveCorrespondingTestClass).check(productionClasses);
}