Mockito - 异常处理

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Mockito 为模拟提供了抛出异常的功能，因此可以测试异常处理。看一下下面的代码片段。

//add the behavior to throw exception
doThrow(new Runtime Exception("divide operation not implemented"))
   .when(calcService).add(10.0,20.0);

这里我们向模拟对象添加了一个异常子句。MathApplication 通过其 add 方法来使用 calcService，并且每当调用 calcService.add() 方法时，模拟都会抛出 RuntimeException。

例子

步骤 1 - 创建一个名为 CalculatorService 的接口来提供数学函数

文件：CalculatorService.java

public interface CalculatorService {
   public double add(double input1, double input2);
   public double subtract(double input1, double input2);
   public double multiply(double input1, double input2);
   public double divide(double input1, double input2);
}

步骤 2 - 创建一个 JAVA 类来表示 MathApplication

文件：MathApplication.java

public class MathApplication {
   private CalculatorService calcService;

   public void setCalculatorService(CalculatorService calcService){
      this.calcService = calcService;
   }
   
   public double add(double input1, double input2){
      return calcService.add(input1, input2);		
   }
   
   public double subtract(double input1, double input2){
      return calcService.subtract(input1, input2);
   }
   
   public double multiply(double input1, double input2){
      return calcService.multiply(input1, input2);
   }
   
   public double divide(double input1, double input2){
      return calcService.divide(input1, input2);
   }
}

步骤 3 - 测试 MathApplication 类

让我们通过向其中注入calculatorService 的模拟来测试MathApplication 类。Mock 将由 Mockito 创建。

文件：MathApplicationTester.java

import static org.mockito.Mockito.doThrow;

import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.runners.MockitoJUnitRunner;

// @RunWith attaches a runner with the test class to initialize the test data
@RunWith(MockitoRunner.class)
public class MathApplicationTester {
	
   // @TestSubject annotation is used to identify class 
      which is going to use the mock object
   @TestSubject
   MathApplication mathApplication = new MathApplication();

   //@Mock annotation is used to create the mock object to be injected
   @Mock
   CalculatorService calcService;

   @Test(expected = RuntimeException.class)
   public void testAdd(){
      //add the behavior to throw exception
      doThrow(new RuntimeException("Add operation not implemented"))
         .when(calcService).add(10.0,20.0);

      //test the add functionality
      Assert.assertEquals(mathApplication.add(10.0, 20.0),30.0,0); 
   }
}

步骤 4 - 执行测试用例

在C:\> Mockito_WORKSPACE中创建一个名为 TestRunner 的 java 类文件来执行测试用例。

文件：TestRunner.java

import org.junit.runner.JUnitCore;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;

public class TestRunner {
   public static void main(String[] args) {
      Result result = JUnitCore.runClasses(MathApplicationTester.class);
      
      for (Failure failure : result.getFailures()) {
         System.out.println(failure.toString());
      }
      
      System.out.println(result.wasSuccessful());
   }
}  	

第 5 步 - 验证结果

使用javac编译器编译类，如下所示 -

C:\Mockito_WORKSPACE>javac CalculatorService.java MathApplication.
   java MathApplicationTester.java TestRunner.java

现在运行测试运行程序来查看结果 -

C:\Mockito_WORKSPACE>java TestRunner

验证输出。

testAdd(MathApplicationTester): Add operation not implemented
false