Mockito – 回撥

Mockito 提供了一個 Answer 介面，它允許用通用介面進行存根。

語法

//add the behavior to add numbers
when(calcService.add(20.0,10.0)).thenAnswer(new Answer<Double>() {
   @Override
   public Double answer(InvocationOnMock invocation) throws Throwable {
      //get the arguments passed to mock
      Object[] args = invocation.getArguments();
      //get the mock 
      Object mock = invocation.getMock();	
      //return the result
      return 30.0;
   }
});

示例

步驟 1 − 建立一個名為 CalculatorService 的介面，提供數學函式

檔案：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);
}

步驟 2 − 建立一個 JAVA 類，表示 MathApplication

檔案：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);
   }
}

步驟 3 − 測試 MathApplication 類

透過向其中注入 calculatorService 的模擬，讓我們測試 MathApplication 類。模擬將由 Mockito 建立。

在此，我們添加了一個模擬方法呼叫 adds()，透過 when() 新增到模擬物件。然而，在測試過程中，我們在呼叫 add() 之前呼叫了 subtract()。當我們使用 Mockito.createStrictMock() 建立模擬物件時，方法的執行順序很重要。

檔案：MathApplicationTester.java

import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
import static org.mockito.Mockito.inOrder;

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InOrder;
import org.mockito.runners.MockitoJUnitRunner;

// @RunWith attaches a runner with the test class to initialize the test data
@RunWith(MockitoJUnitRunner.class)
public class MathApplicationTester {
	
   private MathApplication mathApplication;
   private CalculatorService calcService;

   @Before
   public void setUp(){
      mathApplication = new MathApplication();
      calcService = mock(CalculatorService.class);
      mathApplication.setCalculatorService(calcService);
   }

   @Test
   public void testAdd(){

      //add the behavior to add numbers
      when(calcService.add(20.0,10.0)).thenAnswer(new Answer<Double>() {

         @Override
         public Double answer(InvocationOnMock invocation) throws Throwable {
            //get the arguments passed to mock
            Object[] args = invocation.getArguments();
			
            //get the mock 
            Object mock = invocation.getMock();	
			
            //return the result
            return 30.0;
         }
      });

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

步驟 4 − 執行測試用例

在 **C:\> Mockito_WORKSPACE** 中建立一個名為 TestRunner 的 java 類檔案來執行測試用例。

檔案：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());
   }
}  	

步驟 5 − 驗證結果

使用 **javac** 編譯器編譯類，如下所示 −

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

現在執行測試執行器以檢視結果 −

C:\Mockito_WORKSPACE>java TestRunner

驗證輸出。

true