无需使用 easymock 注入模拟

Question

我想使用 easymock 3.5 和 JUnit5 编写一个小示例，但是在尝试注入模拟时出现错误 (nullPointerException)...

这里是测试代码：

package model;

import controler.BookEditor;
import org.easymock.EasyMockRule;
import org.easymock.EasyMockSupport;
import org.easymock.Mock;
import org.easymock.TestSubject;
import org.junit.Before;
import org.junit.Rule;
import org.junit.jupiter.api.Test;
import view.BookWindow;

import static org.junit.jupiter.api.Assertions.assertEquals;

//@TestInstance(TestInstance.Lifecycle.PER_CLASS)
public class BookTest extends EasyMockSupport {

@Rule
public EasyMockRule rule = new EasyMockRule(this);


@Mock
public BookWindow bookWindow;

public BookList bookList;

@TestSubject
public BookEditor bookEditor;

@Before
public void setUp() {
  bookList = new BookList();
  bookEditor = new BookEditor(bookList, bookWindow);
}

@Test
public void testBookCreation() {

  Book le_livre_de_la_jungle = new Book("Le livre de la jungle", "Rudyard Kipling",
        "Flammarion",
        "978-2081263246");
  assertEquals(le_livre_de_la_jungle.getTitle(), "Le livre de la jungle");
  assertEquals(le_livre_de_la_jungle.getAuthor(), "Rudyard Kipling");
  assertEquals(le_livre_de_la_jungle.getEditor(), "Flammarion");
  assertEquals(le_livre_de_la_jungle.getISBN(), "978-2081263246");

}


@Test
public void testDisplayBook() {
  bookWindow.setTitle("Le livre de la jungle"); //here is line 53
  bookWindow.setAuthor("Rudyard Kipling");
  bookWindow.setEditor("Flammarion");
  bookWindow.setISBN("978-2081263246");
  replayAll();

  bookEditor.setActiveBook(new Book("Le livre de la jungle",
        "Rudyard Kipling", "Flammarion", "978-2081263246"));
  verifyAll();

}

}

第一次测试没问题，但是testDisplayBook失败了，因为bookWindow为null。

在我的 POM 中，我有这个：

<dependencies>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-api</artifactId>
        <version>RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.junit.platform</groupId>
        <artifactId>junit-platform-launcher</artifactId>
        <version>RELEASE</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-engine</artifactId>
        <version>RELEASE</version>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.junit.vintage</groupId>
        <artifactId>junit-vintage-engine</artifactId>
        <version>4.12.1</version>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.junit.platform</groupId>
        <artifactId>junit-platform-runner</artifactId>
        <version>RELEASE</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.easymock</groupId>
        <artifactId>easymock</artifactId>
        <version>3.5</version>
        <scope>test</scope>
    </dependency>

</dependencies>

这里是例外：

java.lang.NullPointerException at model.BookTest.testDisplayBook(BookTest.java:53) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:389) at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:115) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod(TestMethodTestDescriptor.java:167) at org.junit.jupiter.engine.execution.ThrowableCollector.execute(ThrowableCollector.java:40) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:163) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:110) at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:57) at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$execute(HierarchicalTestExecutor.java:83) at org.junit.platform.engine.support.hierarchical.SingleTestExecutor.executeSafely(SingleTestExecutor.java:66) at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:77) at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$null(HierarchicalTestExecutor.java:92)

谢谢。

Answer 1

在 JUnit 5 中 Rules 不能再使用了。你必须 use an Extension and annotate the test class or method with ExtendWith. Furthermore you have to use @BeforeEach instead of @Before (See also the migration section in the user guide).

更新： 从 EasyMock 4.1 开始，EasyMock 附带了一个开箱即用的 JUnit 5 extension。

~~据我所知还没有正式的 EasyMock 扩展。~~ 幸运的是 EasyMockRule 可以很容易地移植：

import org.easymock.EasyMockSupport;
import org.junit.jupiter.api.extension.ExtensionContext;
import org.junit.jupiter.api.extension.TestInstancePostProcessor;

public class EasyMockExtension implements TestInstancePostProcessor {

    @Override
    public void postProcessTestInstance(Object testInstance, ExtensionContext context) throws Exception {
        EasyMockSupport.injectMocks(testInstance);
    }
}

现在您可以为测试添加注释 class:

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.extension.ExtendWith;

// ...

@ExtendWith(EasyMockExtension.class)
public class BookTest extends EasyMockSupport {

    @Mock
    public BookWindow bookWindow;

    public BookList bookList;

    @TestSubject
    public BookEditor bookEditor;

    @BeforeEach
    public void setUp() {
        bookList = new BookList();
        bookEditor = new BookEditor(bookList, bookWindow);
    }

    // ...

Answer 2

使用 JUnit Jupiter 的方法

我认为您的代码的问题之一是它混合使用了 JUnit 4 和 JUnit 5 注释。根据您的堆栈跟踪，我相信您使用的是 JUnit 5 测试引擎，因此您应该将注释 @Before 替换为 @BeforeEach。

我使用支持 JUnit 的 Eclipse Oxygen 重现了您的问题。我通过用显式实例化替换基于注解的注入来超越 NullPointerException：

public class BookTest extends EasyMockSupport {
    public BookWindow bookWindow;
    public BookList bookList;
    public BookEditor bookEditor;

    @BeforeEach
    public void setUp() {
        bookWindow = EasyMock.mock(BookWindow.class);
        bookList = new BookList();
        bookEditor = new BookEditor(bookList, bookWindow);
    }
    ...
}

我没有 Book、BookList、BookEditor 和 BookWindow 的实现，所以我无法验证测试是否通过，但至少它通过了运行并可以定义 bookWindow。

使用 JUnit 4 的方法

话虽如此，我尝试使用 JUnit 4 执行您的代码（将 JUnit Jupiter @Test 注释替换为 @org.junit.Test。这产生了以下异常：

java.lang.NullPointerException: Have you forgotten to instantiate bookEditor?
at org.easymock.internal.Injector.injectMocks(Injector.java:81)
at org.easymock.EasyMockSupport.injectMocks(EasyMockSupport.java:561)
at org.easymock.internal.EasyMockStatement.evaluate(EasyMockStatement.java:42)
...

EasyMock 检查 @TestSubject 在注入模拟之前实例化。我相信您不想实例化 BookEditor before 注入模拟，因为无论如何您最终都会得到 null bookWindow：

public class BookTest extends EasyMockSupport {
    ...
    @Mock
    public BookWindow bookWindow;

    @TestSubject // BookWindow would be null below as not yet injected.
    public BookEditor bookEditor = new BookEditor(bookList, bookWindow);

一种可能是从 bookEditor 实例变量中删除 @TestSubject 注释，并在 @Before 方法中实例化 BookEditor （正如您目前所做的那样） :

public class BookTest extends EasyMockSupport {
    @Rule
    public EasyMockRule rule = new EasyMockRule(this);

    @Mock
    public BookWindow bookWindow;

    public BookList bookList;

    public BookEditor bookEditor;

    @Before
    public void setUp() {
        bookList = new BookList();
        bookEditor = new BookEditor(bookList, bookWindow);
    }
    ...

但是你可能需要@TestSubject，在这种情况下这个解决方案是不可行的。

另一种方法是避免 @Mock 注释并显式实例化模拟：

public class BookTest extends EasyMockSupport {
    ...
    public BookWindow bookWindow = EasyMock.mock(BookWindow.class);

    @TestSubject
    public BookEditor bookEditor = new BookEditor(bookList, bookWindow); 
    ...

无需使用 easymock 注入模拟

no injection of a mock with easymock

java

maven

easymock

junit5