如何在Java8中模拟YearMonth

Question

我正在试着用mockito模仿YearMonth.class。

我调用了getYear和getMonth方法，所以我想控制在我测试的方法中使用的值。然而，我正在讨论以下问题。

org.mockito.exceptions.base.MockitoException: 
Cannot mock/spy class java.time.YearMonth
Mockito cannot mock/spy following:
  - final classes
  - anonymous classes
  - primitive types
    at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl$1.withBefores(JUnit45AndHigherRunnerImpl.java:27)
    at org.junit.runners.BlockJUnit4ClassRunner.methodBlock(BlockJUnit4ClassRunner.java:246)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
    at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
    at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

该测试对mock有以下定义

YearMonth yearMonthMock = mock(YearMonth.class);

我正在测试的方法有以下几点

YearMonth yearMonth = YearMonth.now(ZoneId.of("UTC"));
String year = Integer.toString(yearMonth.getYear());
String month = Integer.toString(yearMonth.getMonthValue());

我如何解决异常以继续使用YearMonth.class，或者我应该使用其他方法。

Answer 1

通过静态方法访问特定于日期和时间的功能是很棘手的。您正在尝试模拟依赖于系统时钟的静态方法。这使得在不采取一些极端措施的情况下很难模拟/监视。(例如更改系统上的时间。lol)

绕过这一问题的一种方法是将对该功能的访问抽象到您可以控制的接口后面。

public interface YearMonthProvider {
    YearMonth now(ZoneId zone);
}

生产环境中的实现可能如下所示

public class SystemYearMonth implements YearMonthProvider {
    public YearMonth now(ZoneId zone) {
        return YearMonth.now(zone);
    }
}

测试中的方法将依赖于抽象而不是具体。

public class MyClass {
    private YearMonthProvider clock;

    public MyClass(YearMonthProvider clock) {
        this.clock = clock;
    }

    public void MyMethod(){
        //...other code

        YearMonth yearMonth = clock.now(ZoneId.of("UTC"));
        String year = Integer.toString(yearMonth.getYear());
        String month = Integer.toString(yearMonth.getMonthValue());

        //... other code
    }
}

这现在允许根据需要灵活地换出依赖项。

在测试中

//Arrange
YearMonth yearMonthStub = YearMonth.of(2016,11);
YearMonthProvider yearMonthMock = mock(YearMonthProvider.class);
when(yearMonthMock.now(ZoneId.of("UTC"))).thenReturn(yearMonthStub);

MyClass sut = new MyClass(yearMonthMock);

//Act
sut.MyMethod();

//Assert
//...