使用 Mockito 模拟新对象创建答案

【问题标题】：Mock new object creation with Mockito使用 Mockito 模拟新对象创建
【发布时间】：2023-02-26 01:50:41
【问题描述】：

每当为该类创建新对象时，我都需要模拟该类对象。我没有使用任何 java 框架来进行依赖注入。下面是我的代码。

加法.java

public int sum(int a, int b) {
    return a + b;
}

应用.java

public int doOperation(int a, int b) {
    Addition addition = new Addition();
    return addition.sum(a, b);
}

应用测试.java

@RunWith(PowerMockRunner.class)
@PrepareForTest(Addition.class)

        Addition addition = PowerMockito.mock(Addition.class);
        PowerMockito.when(addition.sum(ArgumentMatchers.anyInt(), ArgumentMatchers.anyInt())).thenReturn(15);

        PowerMockito.whenNew(Addition.class).withNoArguments().thenReturn(addition);

        Application applicationMock = PowerMockito.mock(Application.class);
        int res = applicationMock.doOperation(1, 5);

        assertEquals(res, 15);

在 Application.java 中，我正在创建 Addition 类实例。我需要返回一个模拟对象而不是一个新对象。当我运行我的应用程序时，我得到 0 作为 res。

java.lang.AssertionError: 
Expected :0
Actual   :15
<Click to see difference>


    at org.junit.Assert.fail(Assert.java:88)
    at org.junit.Assert.failNotEquals(Assert.java:834)
    at org.junit.Assert.assertEquals(Assert.java:645)
    at org.junit.Assert.assertEquals(Assert.java:631)
    at com.dbs.poc.PowerMockAdditionTest.sumWithMocks(PowerMockAdditionTest.java:38)
    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.internal.runners.TestMethod.invoke(TestMethod.java:68)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:326)
    at org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:89)
    at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:97)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:310)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:131)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.access$100(PowerMockJUnit47RunnerDelegateImpl.java:59)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner$TestExecutorStatement.evaluate(PowerMockJUnit47RunnerDelegateImpl.java:147)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.evaluateStatement(PowerMockJUnit47RunnerDelegateImpl.java:107)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:298)
    at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:87)
    at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:50)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:218)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:160)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:134)
    at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)
    at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:136)
    at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:117)
    at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:57)
    at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:59)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

【问题讨论】：

您是否尝试过更改代码的位置。像这样 Addition addition = PowerMockito.mock(Addition.class);应用程序 applicationMock = PowerMockito.mock(Application.class); PowerMockito.whenNew(Addition.class).withNoArguments().thenReturn(加法); PowerMockito.when(addition.sum(ArgumentMatchers.anyInt(), ArgumentMatchers.anyInt())).thenReturn(15); int res = applicationMock.doOperation(1, 5); assertEquals(res, 15);
你应该不是（或因此）模拟Application！不是模拟：举一个真实的例子。因此：当你模拟时，确保你的模拟做new Addition()#sum()，因为“默认模拟”（安静而温和地）返回空值和0s（什么都不做）。
你应该改变你的设计并使用工厂
@HarshMishra，我试过你的方法。但不起作用。
@xerx593 当我使用真实实例时，它正在进行真实处理，这意味着 Addition.java 中的逻辑正在执行并返回原始结果而不是模拟结果。例如：在上面的代码中它返回 6 但模拟的是 15。

标签： java junit mockito powermockito

【解决方案1】：

你少了一行。尝试这个。

 Application applicationMock = PowerMockito.mock(Application.class);
 PowerMockito.when(applicationMock.doOperation(anyInt(), anyInt())).thenCallRealMethod();
 int res = applicationMock.doOperation(1, 5);

您已将应用程序声明为 Mock。并且没有定义 doOperation 方法的行为。因此控件不会进入该方法，因此没有任何效果。

这是完整的代码，

@RunWith(PowerMockRunner.class)
@PrepareForTest({Application.class})
public class ApplicationTest {

    @Test
    public void test() throws Exception {
        Addition addition = PowerMockito.mock(Addition.class);
        PowerMockito.when(addition.sum(ArgumentMatchers.anyInt(), ArgumentMatchers.anyInt())).thenReturn(15);

    PowerMockito.whenNew(Addition.class).withNoArguments().thenReturn(addition);

        Application applicationMock = PowerMockito.mock(Application.class);
        when(applicationMock.doOperation(anyInt(), anyInt())).thenCallRealMethod();
        int res = applicationMock.doOperation(1, 5);

        assertEquals(res, 15);
    }
}

如果您只想测试加法方法。您不需要模拟 Application 类。而是创建 Application 类的新实例。这样您就不需要修复，您当前的代码就足够了。

使用

Application application = new Application();

代替

Application applicationMock = PowerMockito.mock(Application.class);

如果您有正当理由使用模拟而不是真实实例，那么这就是解决方案。

【讨论】：

如果 Application 是被测类，则不应模拟它。请改用真实实例。
这可能是因为 Powermockito 的误用（过度使用）。只是指出不应模拟被测试的类

【解决方案2】：

这是问题/缺失的链接：

Application applicationMock = PowerMockito.mock(Application.class);
int res = applicationMock.doOperation(1, 5);

applicationMock.doOperation(x, y) 是什么意思？ - 什么都不返回 0。（您可以配置 (Power)mock(ito) 来抛出异常 -> “strict mock”）

你想要的是：

a) 测试“真实Application”（无模拟）：

Application testApp = new Applicaiton();
int res = testApp.doOperation(1, 5);
// ...

或者 b）“编程”你的模拟，伪造/复制真正的实现（例如@pvpkiran 概述）：

Application applicationMock = PowerMockito.mock(Application.class);
PowerMockito.when(applicationMock.doOperation(anyInt(), anyInt())).then...

【讨论】：