小架構step系列13：測試用例的加載

1 概述

測試用例的編寫要有一些基礎的規范，在本文先定義文件名稱和測試用例方法名的規范。

2 文件加載原理

先從源碼來看一下測試用例的文件加載原理。

2.1 文件的匹配

主要是通過注解來掃描測試用例。

// 在IDEA測試用例啟動時，調用junit-platform-launcher-x.x.x.jar包里的類啟動，最終會調JupiterTestEngine.discover()來加載測試用例
// 估計在不同的地方，啟動的方式可能有所不同，junit-platform-launcher-x.x.x.jar包并沒有引入到工程里
// 源碼位置：org.junit.jupiter.engine.JupiterTestEngine
public TestDescriptor discover(EngineDiscoveryRequest discoveryRequest, UniqueId uniqueId) {JupiterConfiguration configuration = new CachingJupiterConfiguration(new DefaultJupiterConfiguration(discoveryRequest.getConfigurationParameters()));JupiterEngineDescriptor engineDescriptor = new JupiterEngineDescriptor(uniqueId, configuration);// 1. 先在DiscoverySelectorResolver()初始化resolver，然后使用resolver去加載測試用例new DiscoverySelectorResolver().resolveSelectors(discoveryRequest, engineDescriptor);return engineDescriptor;
}// 源碼位置：org.junit.jupiter.engine.discovery.DiscoverySelectorResolver
public class DiscoverySelectorResolver {// 初始化多個resolverprivate static final EngineDiscoveryRequestResolver<JupiterEngineDescriptor> resolver = EngineDiscoveryRequestResolver.<JupiterEngineDescriptor>builder()// 2. 設置加載測試用例文件的ClassContainerSelectorResolver，IsTestClassWithTests是最終的過濾類ClassFilter.addClassContainerSelectorResolver(new IsTestClassWithTests()) .addSelectorResolver(context -> new ClassSelectorResolver(context.getClassNameFilter(), context.getEngineDescriptor().getConfiguration())).addSelectorResolver(context -> new MethodSelectorResolver(context.getEngineDescriptor().getConfiguration())).addTestDescriptorVisitor(context -> new ClassOrderingVisitor(context.getEngineDescriptor().getConfiguration())).addTestDescriptorVisitor(context -> new MethodOrderingVisitor(context.getEngineDescriptor().getConfiguration())).addTestDescriptorVisitor(context -> TestDescriptor::prune).build();public void resolveSelectors(EngineDiscoveryRequest request, JupiterEngineDescriptor engineDescriptor) {resolver.resolve(request, engineDescriptor);}
}// 源碼位置：org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolver.Builder
public Builder<T> addClassContainerSelectorResolver(Predicate<Class<?>> classFilter) {Preconditions.notNull(classFilter, "classFilter must not be null");// 3. 把ClassFilter包到ClassContainerSelectorResolver里面，這個ClassFilter是IsTestClassWithTestsreturn addSelectorResolver(context -> new ClassContainerSelectorResolver(classFilter, context.getClassNameFilter()));
}
public Builder<T> addSelectorResolver(Function<InitializationContext<T>, SelectorResolver> resolverCreator) {// 4. ClassContainerSelectorResolver最終存儲在resolverCreators變量里resolverCreators.add(resolverCreator);return this;
}// 回到DiscoverySelectorResolver，調用resolveSelectors()
// 源碼位置：org.junit.jupiter.engine.discovery.DiscoverySelectorResolver
public class DiscoverySelectorResolver {// 初始化多個resolverprivate static final EngineDiscoveryRequestResolver<JupiterEngineDescriptor> resolver = EngineDiscoveryRequestResolver.<JupiterEngineDescriptor>builder()// 2. 設置加載測試用例文件的ClassContainerSelectorResolver，IsTestClassWithTests是最終的過濾類ClassFilter.addClassContainerSelectorResolver(new IsTestClassWithTests()) .addSelectorResolver(context -> new ClassSelectorResolver(context.getClassNameFilter(), context.getEngineDescriptor().getConfiguration())).addSelectorResolver(context -> new MethodSelectorResolver(context.getEngineDescriptor().getConfiguration())).addTestDescriptorVisitor(context -> new ClassOrderingVisitor(context.getEngineDescriptor().getConfiguration())).addTestDescriptorVisitor(context -> new MethodOrderingVisitor(context.getEngineDescriptor().getConfiguration())).addTestDescriptorVisitor(context -> TestDescriptor::prune).build();public void resolveSelectors(EngineDiscoveryRequest request, JupiterEngineDescriptor engineDescriptor) {5. 執行resolver.resolve加載測試用例resolver.resolve(request, engineDescriptor);}
}// 源碼位置：org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolver
public void resolve(EngineDiscoveryRequest request, T engineDescriptor) {Preconditions.notNull(request, "request must not be null");Preconditions.notNull(engineDescriptor, "engineDescriptor must not be null");InitializationContext<T> initializationContext = new DefaultInitializationContext<>(request, engineDescriptor);// 6. 初始化resolver，把resolverCreators作為參數傳入List<SelectorResolver> resolvers = instantiate(resolverCreators, initializationContext);List<TestDescriptor.Visitor> visitors = instantiate(visitorCreators, initializationContext);new EngineDiscoveryRequestResolution(request, engineDescriptor, resolvers, visitors).run();
}// 源碼位置：org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolver
private <R> List<R> instantiate(List<Function<InitializationContext<T>, R>> creators, InitializationContext<T> context) {// 7. 遍歷Resolver執行lambda表達式函數，這個函數執行的時候，就是執行Resolver的resolve接口，//    其中重點在于ClassContainerSelectorResolver，里面放了IsTestClassWithTests這個ClassFilter，通過該類進行過濾return creators.stream().map(creator -> creator.apply(context)).collect(toCollection(ArrayList::new));
}// 回到EngineDiscoveryRequestResolver
// 源碼位置：org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolver
public void resolve(EngineDiscoveryRequest request, T engineDescriptor) {Preconditions.notNull(request, "request must not be null");Preconditions.notNull(engineDescriptor, "engineDescriptor must not be null");InitializationContext<T> initializationContext = new DefaultInitializationContext<>(request, engineDescriptor);// 6. 初始化resolver，把resolverCreators作為參數傳入List<SelectorResolver> resolvers = instantiate(resolverCreators, initializationContext);List<TestDescriptor.Visitor> visitors = instantiate(visitorCreators, initializationContext);// 8. 執行resolvernew EngineDiscoveryRequestResolution(request, engineDescriptor, resolvers, visitors).run();
}// 源碼位置：org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution
void run() {remainingSelectors.addAll(request.getSelectorsByType(DiscoverySelector.class));while (!remainingSelectors.isEmpty()) {// 9. 執行，參數為ClasspathRootSelector，里面放了測試用例class文件的根目錄，如果是IDEA環境則是target/test-classes目錄resolveCompletely(remainingSelectors.poll());}visitors.forEach(engineDescriptor::accept);
}
private void resolveCompletely(DiscoverySelector selector) {EngineDiscoveryListener discoveryListener = request.getDiscoveryListener();UniqueId engineId = engineDescriptor.getUniqueId();try {// 10. 執行，參數為ClasspathRootSelectorOptional<Resolution> result = resolve(selector);if (result.isPresent()) {discoveryListener.selectorProcessed(engineId, selector, resolved());enqueueAdditionalSelectors(result.get());}else {discoveryListener.selectorProcessed(engineId, selector, unresolved());}}catch (Throwable t) {UnrecoverableExceptions.rethrowIfUnrecoverable(t);discoveryListener.selectorProcessed(engineId, selector, failed(t));}
}// 源碼位置：org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution
private Optional<Resolution> resolve(DiscoverySelector selector) {if (resolvedSelectors.containsKey(selector)) {return Optional.of(resolvedSelectors.get(selector));}if (selector instanceof UniqueIdSelector) {return resolveUniqueId((UniqueIdSelector) selector);}// 11. 執行resolver，重點關注ClassContainerSelectorResolverreturn resolve(selector, resolver -> {Context context = getContext(selector);if (selector instanceof ClasspathResourceSelector) {return resolver.resolve((ClasspathResourceSelector) selector, context);}if (selector instanceof ClasspathRootSelector) {return resolver.resolve((ClasspathRootSelector) selector, context);}if (selector instanceof ClassSelector) {return resolver.resolve((ClassSelector) selector, context);}if (selector instanceof NestedClassSelector) {return resolver.resolve((NestedClassSelector) selector, context);}if (selector instanceof DirectorySelector) {return resolver.resolve((DirectorySelector) selector, context);}if (selector instanceof FileSelector) {return resolver.resolve((FileSelector) selector, context);}if (selector instanceof MethodSelector) {return resolver.resolve((MethodSelector) selector, context);}if (selector instanceof NestedMethodSelector) {return resolver.resolve((NestedMethodSelector) selector, context);}if (selector instanceof ModuleSelector) {return resolver.resolve((ModuleSelector) selector, context);}if (selector instanceof PackageSelector) {return resolver.resolve((PackageSelector) selector, context);}if (selector instanceof UriSelector) {return resolver.resolve((UriSelector) selector, context);}return resolver.resolve(selector, context);});
}
private Optional<Resolution> resolve(DiscoverySelector selector,Function<SelectorResolver, Resolution> resolutionFunction) {// 12. resolutionFunction是第11步的lambda表達式return resolvers.stream().map(resolutionFunction).filter(Resolution::isResolved).findFirst() // 觸發lambda表達式執行.map(resolution -> {contextBySelector.remove(selector);resolvedSelectors.put(selector, resolution);resolution.getMatches().forEach(match -> resolvedUniqueIds.put(match.getTestDescriptor().getUniqueId(), match));return resolution;});
}// 源碼位置：org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution
private Optional<Resolution> resolve(DiscoverySelector selector) {if (resolvedSelectors.containsKey(selector)) {return Optional.of(resolvedSelectors.get(selector));}if (selector instanceof UniqueIdSelector) {return resolveUniqueId((UniqueIdSelector) selector);}// 11. 執行resolver，重點關注ClassContainerSelectorResolverreturn resolve(selector, resolver -> {Context context = getContext(selector);if (selector instanceof ClasspathResourceSelector) {return resolver.resolve((ClasspathResourceSelector) selector, context);}if (selector instanceof ClasspathRootSelector) {// 13. 執行resolver的resolve()方法return resolver.resolve((ClasspathRootSelector) selector, context);}if (selector instanceof ClassSelector) {return resolver.resolve((ClassSelector) selector, context);}if (selector instanceof NestedClassSelector) {return resolver.resolve((NestedClassSelector) selector, context);}if (selector instanceof DirectorySelector) {return resolver.resolve((DirectorySelector) selector, context);}if (selector instanceof FileSelector) {return resolver.resolve((FileSelector) selector, context);}if (selector instanceof MethodSelector) {return resolver.resolve((MethodSelector) selector, context);}if (selector instanceof NestedMethodSelector) {return resolver.resolve((NestedMethodSelector) selector, context);}if (selector instanceof ModuleSelector) {return resolver.resolve((ModuleSelector) selector, context);}if (selector instanceof PackageSelector) {return resolver.resolve((PackageSelector) selector, context);}if (selector instanceof UriSelector) {return resolver.resolve((UriSelector) selector, context);}return resolver.resolve(selector, context);});
}// 源碼位置：org.junit.platform.engine.support.discovery.ClassContainerSelectorResolver
public Resolution resolve(ClasspathRootSelector selector, Context context) {return classSelectors(findAllClassesInClasspathRoot(selector.getClasspathRoot(), classFilter, classNameFilter));
}
private SelectorResolver.Resolution classSelectors(List<Class<?>> classes) {return classes.isEmpty() ? Resolution.unresolved() : Resolution.selectors((Set)classes.stream().map(DiscoverySelectors::selectClass).collect(Collectors.toSet()));
}
public static List<Class<?>> findAllClassesInClasspathRoot(URI root, Predicate<Class<?>> classFilter, Predicate<String> classNameFilter) {// 14. classFilter即前面提供的IsTestClassWithTests，查找指定目錄(root)的類文件，并通過classFilter過濾//     ReflectionUtils里使用classpathScanner掃描測試用例文件，調用classFilter的test()方法進行過濾return ReflectionUtils.findAllClassesInClasspathRoot(root, classFilter, classNameFilter);
}
// 源碼位置：org.junit.platform.commons.util.ReflectionUtils
public static List<Class<?>> findAllClassesInClasspathRoot(URI root, Predicate<Class<?>> classFilter, Predicate<String> classNameFilter) {return findAllClassesInClasspathRoot(root, ClassFilter.of(classNameFilter, classFilter));
}
public static List<Class<?>> findAllClassesInClasspathRoot(URI root, ClassFilter classFilter) {return Collections.unmodifiableList(classpathScanner.scanForClassesInClasspathRoot(root, classFilter));
}// 源碼位置：org.junit.jupiter.engine.discovery.predicates.IsTestClassWithTests
public class IsTestClassWithTests implements Predicate<Class<?>> {// 根據方法上有@Test注解過濾private static final IsTestMethod isTestMethod = new IsTestMethod();// 根據有@TestFactory注解過濾private static final IsTestFactoryMethod isTestFactoryMethod = new IsTestFactoryMethod();// 根據有@TestTemplate注解過濾private static final IsTestTemplateMethod isTestTemplateMethod = new IsTestTemplateMethod();// 15. 執行過濾public boolean test(Class<?> candidate) {return isPotentialTestContainer.test(candidate)&& (hasTestOrTestFactoryOrTestTemplateMethods(candidate) || hasNestedTests(candidate));}// 省略其它代碼
}// 源碼位置：org.junit.jupiter.engine.discovery.predicates.IsTestMethod
public class IsTestMethod extends IsTestableMethod {public IsTestMethod() {super(Test.class, true); // @Test注解}
}
// 源碼位置：org.junit.jupiter.engine.discovery.predicates.IsTestFactoryMethod
public class IsTestFactoryMethod extends IsTestableMethod {public IsTestFactoryMethod() {super(TestFactory.class, false); //@TestFactory注解}
}
// 源碼位置：org.junit.jupiter.engine.discovery.predicates.IsTestTemplateMethod
public class IsTestTemplateMethod extends IsTestableMethod {public IsTestTemplateMethod() {super(TestTemplate.class, true); // @TestTemplate注解}
}// org.junit.jupiter.engine.discovery.predicates.IsTestableMethod
abstract class IsTestableMethod implements Predicate<Method> {private final Class<? extends Annotation> annotationType;private final boolean mustReturnVoid;IsTestableMethod(Class<? extends Annotation> annotationType, boolean mustReturnVoid) {this.annotationType = annotationType;this.mustReturnVoid = mustReturnVoid;}@Overridepublic boolean test(Method candidate) {// Please do not collapse the following into a single statement.if (isStatic(candidate)) { // 不支持靜態方法的測試用例return false;}if (isPrivate(candidate)) { // 不支持私有方法的測試用例return false;}if (isAbstract(candidate)) { // 不支持抽象方法的測試用例return false;}if (returnsVoid(candidate) != this.mustReturnVoid) { // 不支持返回值不是Void的測試用例return false;}// 16. 根據注解過濾return isAnnotated(candidate, this.annotationType);}
}// org.junit.platform.commons.util.AnnotationUtils
public static boolean isAnnotated(AnnotatedElement element, Class<? extends Annotation> annotationType) {// 17. 查找對應的注解，如果注解存在則是滿足要求的測試用例類//     即帶有@Test、@TestFactory、@TestTemplate這三種注解的測試用例類才是符合要求的測試用例類return findAnnotation(element, annotationType).isPresent();
}// 回到EngineDiscoveryRequestResolution，存儲找到的測試用例
// 源碼位置：org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution
private void resolveCompletely(DiscoverySelector selector) {EngineDiscoveryListener discoveryListener = request.getDiscoveryListener();UniqueId engineId = engineDescriptor.getUniqueId();try {// 10. 執行，參數為ClasspathRootSelectorOptional<Resolution> result = resolve(selector);if (result.isPresent()) {discoveryListener.selectorProcessed(engineId, selector, resolved());// 17. 把找到的測試用例類存到變量中，供后面使用enqueueAdditionalSelectors(result.get());}else {discoveryListener.selectorProcessed(engineId, selector, unresolved());}}catch (Throwable t) {UnrecoverableExceptions.rethrowIfUnrecoverable(t);discoveryListener.selectorProcessed(engineId, selector, failed(t));}
}

2.2 規則

從上面原理看，可以分為文件和方法兩個角度來分析。

從文件角度來說，得有@Test、@TestFactory、@TestTemplate三種注解中的一種，測試用例文件才會被加載到。@TestFactory是用于動態創建多個測試用例，感覺測試用例還是一個個分開寫比較容易維護，此注解爭取不使用。

@TestTemplate注解則可以幫助提供動態參數給測試用例，在某些場景可能需要用，建議封裝到框架里使用。

從方法角度來看，私有方法、靜態方法、抽象方法、有返回值的方法，都不能成為測試用例，需要規避這些情況。

@SpringBootTest
@AutoConfigureMockMvc
public class HelloControllerTest {@Autowiredprivate MockMvc mockMvc;@Testpublic void should_say_string() throws Exception {String messge = "abc";MvcResult result = mockMvc.perform(MockMvcRequestBuilders.post("/sayHello").contentType(MediaType.APPLICATION_FORM_URLENCODED).content("message=" + messge)).andExpect(status().isOk()).andReturn();assertThat(result.getResponse().getContentAsString()).isEqualTo("Hello world: " + messge);}@Testprivate String check_empty_in_private_method() {String str = "abc";assertThat(str).isNotEmpty();return str;}@Testpublic String check_empty_with_return_value() {String str = "abc";assertThat(str).isNotEmpty();return str;}@Testpublic static void check_empty_in_static_method() {String str = "abc";assertThat(str).isNotEmpty();}
}