Archunit enforce test coverage

Question

How can I enforce using Archunit that every class has a correspondent test class?

I'm able to get all the class that I want to check using this Rule:

        classes().that()
                 .areNotInterfaces()
                 .and()
                 .areNotAnonymousClasses()
                 .and()
                 .areNotRecords()
                 .and()
                 .areNotEnums()
                 .should()

But not sure where to go from here.

Thanks

Answer 1

You can implement a "non-local" ArchCondition (i.e. one that relies on all objects to test) by overwriting its init(Collection<T> allObjectsToTest) method.

ArchUnit's library of GeneralCodingRules has a testClassesShouldResideInTheSamePackageAsImplementation(), whose implementation is a good starting point to come up with something like this:

@ArchTest
static final ArchRule relevant_classes_should_have_tests =
        classes()
            .that()
                .areTopLevelClasses()
                .and().areNotInterfaces()
                .and().areNotRecords()
                .and().areNotEnums()
            .should(haveACorrespondingClassEndingWith("Test"));

private static ArchCondition<JavaClass> haveACorrespondingClassEndingWith(String testClassSuffix) {
    return new ArchCondition<JavaClass>("have a corresponding class with suffix " + testClassSuffix) {
        Set<String> testedClasseNames = emptySet();

        @Override
        public void init(Collection<JavaClass> allClasses) {
            testedClasseNames = allClasses.stream()
                    .map(JavaClass::getName)
                    .filter(className -> className.endsWith(testClassSuffix))
                    .map(className -> className.substring(0, className.length() - testClassSuffix.length()))
                    .collect(toSet());
        }

        @Override
        public void check(JavaClass clazz, ConditionEvents events) {
            if (!clazz.getName().endsWith(testClassSuffix)) {
                boolean satisfied = testedClasseNames.contains(clazz.getName());
                String message = createMessage(clazz, "has " + (satisfied ? "a" : "no") + " corresponding test class");
                events.add(new SimpleConditionEvent(clazz, satisfied, message));
            }
        }
    };
}