Faster Sling/AEM tests with JUnit5

SlingContext/AemContext

• allow to create repository and populate it with test data
• provided as JUnit4 @Rule, so context instance is created before every test in class even if it’s unnecessary
• the same ResourceResolverType (eg. JCR_OAK) is used for all tests, even if the faster one (eg. RESOURCERESOLVER_MOCK) is sufficient for some tests

JUnit5

• modern testing framework released in 2017
• allows to write JUnit3, JUnit4 and JUnit5 tests in the same project
• easily extendable by implementing interfaces allowing to inject logic into test lifecycle
• can be used to inject parameter directly to test method:

@Test
void shouldVerifySomething(JcrOakAemContext context) {
    context.addModelsForPackage("co.nums.aem.blog.models");
    context.load().json("co/nums/aem/blog/data/test.json", "/content/blog");
    Resource testResource = context.resourceResolver().getResource("/content/blog/test-node");

    TestModel sut = testResource.adaptTo(TestModel.class);

    // assertions
}

Extension

import io.wcm.testing.mock.aem.context.AemContextImpl;

public class AemContext extends AemContextImpl {
    protected void setUpContext() {
        super.setUp();
    }
    protected void tearDownContext() {
        super.tearDown();
    }
}

import org.apache.sling.testing.mock.sling.ResourceResolverType;

public class ResourceResolverMockAemContext extends AemContext {
    ResourceResolverMockAemContext() {
        setResourceResolverType(ResourceResolverType.RESOURCERESOLVER_MOCK);
    }
}

import org.apache.sling.testing.mock.sling.ResourceResolverType;

public class JcrMockAemContext extends AemContext {
    JcrMockAemContext() {
        setResourceResolverType(ResourceResolverType.JCR_MOCK);
    }
}

import org.apache.sling.testing.mock.sling.ResourceResolverType;

public class JcrOakAemContext extends AemContext {
    JcrOakAemContext() {
        setResourceResolverType(ResourceResolverType.JCR_OAK);
    }
}

import org.junit.jupiter.api.extension.AfterTestExecutionCallback;
import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.ExtensionContext.Namespace;
import org.junit.jupiter.api.extension.ExtensionContext.Store;
import org.junit.jupiter.api.extension.ParameterContext;
import org.junit.jupiter.api.extension.ParameterResolver;

import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Supplier;

import static java.util.Collections.unmodifiableMap;

public class AemContextProvider implements ParameterResolver, AfterTestExecutionCallback {

    private static final Namespace AEM_CONTEXT_NAMESPACE = Namespace.create(AemContextProvider.class);

    private static final Map<Type, Supplier<? extends AemContext>> CONTEXT_SUPPLIERS;
    static {
        Map<Type, Supplier<? extends AemContext>> suppliers = new HashMap<>();
        suppliers.put(ResourceResolverMockAemContext.class, ResourceResolverMockAemContext::new);
        suppliers.put(JcrMockAemContext.class, JcrMockAemContext::new);
        suppliers.put(JcrOakAemContext.class, JcrOakAemContext::new);
        CONTEXT_SUPPLIERS = unmodifiableMap(suppliers);
    }

    @Override
    public boolean supportsParameter(ParameterContext parameterContext, ExtensionContext extensionContext) {
        return CONTEXT_SUPPLIERS.containsKey(parameterContext.getParameter().getType());
    }

    @Override
    public Object resolveParameter(ParameterContext parameterContext, ExtensionContext extensionContext) {
        AemContext aemContext = CONTEXT_SUPPLIERS.get(parameterContext.getParameter().getType()).get();
        aemContext.setUpContext();
        getStore(extensionContext).put(extensionContext.getRequiredTestMethod(), aemContext);
        return aemContext;
    }

    @Override
    public void afterTestExecution(ExtensionContext extensionContext) {
        AemContext aemContext = getAemContext(extensionContext);
        if (aemContext != null) {
            aemContext.tearDownContext();
        }
    }

    private AemContext getAemContext(ExtensionContext extensionContext) {
        return getStore(extensionContext).get(extensionContext.getRequiredTestMethod(), AemContext.class);
    }

    private Store getStore(ExtensionContext context) {
        return context.getStore(AEM_CONTEXT_NAMESPACE);
    }
}

Speed comparison

• compared JUnit4 and JUnit5 test classes with:
  • 2 empty test methods using JCR_OAK context
  • 20 empty test methods using RESOURCERESOLVER_MOCK context
  • 10 empty test methods without using context
• JUnit4:
  • run from IntelliJ IDEA: 9.276s
  • run with mvn clean test: 8.696s
• JUnit5:
  • run from IntelliJ IDEA: 2.116s
  • run with mvn clean test: 1.892s
• only one class per JUnit4/JUnit5 was tested and ~1.5s is the time of creating AEM context for the first time, so once it is ready, next tests will be faster by about 15-20x (assuming that tests will use similar resource resolvers)
• build speed improvement is significant

Source code

• here you go

Notes

• if project has JUnit3/JUnit4 and JUnit5 tests, then 2 engines (Jupiter and Vintage) are run during the build, so time earned on tests level can be stolen by second engine execution (few seconds of overhead) - it’s recommended to write only JUnit5 tests in new projects and migrate tests in existing ones
• the same approach can be used for Sling Mocks (and other Sling-related mocks)