Mockito：如何模拟JodaTime的界面 | 如何模拟JodaTime的界面

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问题描述

我使用 JodaTime＃DateTime ，我需要嘲笑它的行为。由于无法直接模拟 JodaTime＃DateTime ，我创建了它的接口

I use JodaTime#DateTime, and I need to mock its behavior. Since it is not possible to directly mock JodaTime#DateTime, I create an interface of it

Clock.java

public interface Clock {
    DateTime getCurrentDateTimeEST();
    DateTime getFourPM_EST();
    DateTime getSevenPM_EST();
}

JodaTime.java

public class JodaTime implements Clock {

    @Override
    public DateTime getCurrentDateTimeEST() {
        return new DateTime(DateTimeZone.forID("EST"));
    }

    @Override
    public DateTime getFourPM_EST() {
        DateTime current = getCurrentDateTimeEST();
        return new DateTime(current.getYear(), current.getMonthOfYear(),
                current.getDayOfMonth(), 16, 0, 0, 0, DateTimeZone.forID("EST"));
    }

    @Override
    public DateTime getSevenPM_EST() {
        DateTime current = getCurrentDateTimeEST();
        return new DateTime(current.getYear(), current.getMonthOfYear(),
                current.getDayOfMonth(), 19, 0, 0, 0, DateTimeZone.forID("EST"));
    }
}

这是我要测试的方法

public class PrintProcessor{

  Clock jodaTime;

  public PrintProcessor(){
      jodaTime = new JodaTime();
  }
  ...
  public String getPrintJobName(Shipper shipper){
    String printJobName = null;
    //Get current EST time
    if(jodaTime.getCurrentDateTimeEST().isBefore(jodaTime.getFourPM_EST()) ||
            jodaTime.getCurrentDateTimeEST().isAfter(jodaTime.getSevenPM_EST())){   //Before 4PM EST and after 7PM EST
        switch(shipper){
        case X:
        ...
    }else if(jodaTime.getCurrentDateTimeEST().isBefore(jodaTime.getSevenPM_EST())){ //Between 4PM-7PM EST
        switch(shipper){
        case X:
        ...
    }
    return printJobName;
  }
}

正如您所见 printJobName 取决于当天的当前时间相对于时间间隔[4 PM-7PM] EST和出货单名称。由于Shipper将通过参数传递，我们可以对它进行单元测试没问题。但我需要嘲笑时间。所以这是我尝试的东西

As you can see the printJobName depend on the current time of the day relative to the time interval [4PM-7PM] EST and the Shipper name. Since Shipper will be pass via parameter, we can unit test it no problem. But I need to mock the time. So here is what I try

@Test
public void testGetPrintJobNameBeforeFourPM(){
    DateTime current = new DateTime(DateTimeZone.forID("EST"));
    Clock clock = mock(Clock.class);
    //Always return 6pm when I try to ask for the current time
    when(clock.getCurrentDateTimeEST()).thenReturn(new DateTime(current.getYear(), current.getMonthOfYear(),
            current.getDayOfMonth(), 18, 0, 0, 0, DateTimeZone.forID("EST")));
    //Test for Fedex
    String printJobName = printProcessor.getPrintJobName(Shipper.X);
    assertEquals("XNCRMNCF", printJobName);
}

测试应该失败，因为我在下午6点通过，但是 XNCRMNCF 是下午4点之前的名称。我是否还需要模拟 printProcessor 。如果我有什么不对。我应该怎么解决？ 我正在努力学习编写高级java代码，请非常批评我的代码。我真的想学习

The test should fail since I pass in 6PM, but XNCRMNCF is the name for before 4PM. Do I need to mock printProcessor as well. If what I have is wrong. How should I fix it? I am trying to learn writing high level java code, please be very criticized about my code. I really want to learn

推荐答案

这是一个经典的测试案例，显示了设计中的潜在缺陷。你不能模拟 JodaTime ，因为你的被测试阶段对这些类有一个硬连线依赖。

This is a classic case of testing showing up a potential flaw in design. You cannot mock JodaTime because you have a hard-wired dependency to these classes in your class-under-test.

查看，了解为什么这可能是一个问题（特别是在这种情况下）。如果您将 JodaTime 作为依赖项注入某处，那么在单元测试中，您将能够用视情况而定。

Have a look at the SOLID principles to understand why this could be a problem (especially in this case the Dependency Inversion Principle). If you injected JodaTime somewhere as a dependency, then in your unit test you would be able to replace a real instace of it with a mock, stub or spy as appropriate.

但是： JodaTime 是一种极不可能在生产环境中注入任何其他内容的东西，无论它存在多长时间。相反，在这种情况下，您可能会更好地使用。在这里，您将提取用于生成 printjobName 的任何计算/算法到另一个方法（我在这里看不到你是怎么做的，因为你的代码片段从不指定一个值到那个变量）。然后你可以间谍（部分模拟）你正在测试的类只模拟那个方法并返回一个固定值，而不管 JodaTime 正在传递的实际日期时间，例如：

However: JodaTime is something that is highly unlikely to be injected with anything else in the production environment, no matter how long it is live for. Instead, in this case you would probably be better served with the Composed Method Design Pattern. Here, you would extract whatever calculation/algorithm you use to generate the printjobName to another method (I can't see how you do it here because your code snippet never assigns a value to that variable). Then you can spy (partial mock) your class under test to only mock that method and return a fixed value, regardless of the real date time that JodaTime is delivering, for instance:

public class PrintProcessor {
    ...
    public String getPrintJobName(Shipper shipper) {
        String printJobName = null;
        String timeHash = this.getTimeHash();
        if (this.isBeforeFourPM()) {
            switch(shipper) {
                printJobName = // Do something with timeHash to generate name
            }
        } else {
            ...
        }
        return printJobName;
    }

    public boolean isBeforeFourPM() {
        return (jodaTime.getCurrentDateTimeEST().isBefore(jodaTime.getFourPM_EST()) ||
            jodaTime.getCurrentDateTimeEST().isAfter(jodaTime.getSevenPM_EST()));
    }

    public String getTimeHash() {
        ... // Do something to hash the time value in to a String
    }
}

现在你可以写下你的测试：

Now you can write in your test:

@Test
public void testGetPrintJobNameBeforeFourPM() {
    PrintProcessor concretePrintProcessor = new PrintProcessor();
    PrintProcessor printProcessor = spy(concretePrintProcessor);
    doReturn(true).when(printProcessor).isBeforeFourPM();

    String printJobName = printProcessor.getPrintJobName(Shipper.X);

    assertEquals("XNCRMNCF", printJobName);
}

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