mockitoとJMockitについてのメモ ref: http://qiita.com/kazurof/items/1171c7e038050453c6c9

Calc.java

package org.example;

public class Calc {
  int remainder(int dividend, int divisor) {
    return dividend % divisor;
  }
}

Logic.java

package org.example;

public class Logic {
  Calc calc;

  Logic(Calc calc) {
    this.calc = calc;
  }
  /**割り切れる数字のペアをアトランダムに返す。*/
  int[] getDivisibleNumbers() {
    while (true) {
      int candidate = (int) (Math.random() * 100) + 1;
      int candidate2 = (int) (Math.random() * 10) + 1;
      if (calc.remainder(candidate, candidate2) == 0) {
        return new int[]{candidate, candidate2};
      }
    }
  }
}

LogicTestInJMockit.java

package org.example;

import mockit.Expectations;
import mockit.Mocked;
import mockit.Verifications;
import mockit.integration.junit4.JMockit;
import org.junit.Test;
import org.junit.runner.RunWith;

import static org.junit.Assert.assertTrue;

@RunWith(JMockit.class)
public class LogicTestInJMockit {

  @Test
  public void testAsUsual() throws Exception {
    Logic logic = new Logic(new Calc());
    int[] result = logic.getDivisibleNumbers();
    assertTrue(result[0] % result[1] == 0);
  }


  @Test
  public void testInJMockit(@Mocked Calc calc) throws Exception {
    new Expectations() {{
      calc.remainder(anyInt, 5);
      result = 0;
      calc.remainder(anyInt, anyInt);
      result = 1;
    }};
    Logic logic = new Logic(calc);
    int[] result = logic.getDivisibleNumbers();
    new Verifications() {{
      calc.remainder(anyInt, 5);
      minTimes = 1;
    }};
    assertTrue(result[1] == 5);
  }
}

LogicTestInJMockitMockups.java

package org.example;

import mockit.Mock;
import mockit.MockUp;
import org.junit.Test;

import static org.junit.Assert.assertTrue;

public class LogicTestInJMockitMockups {

  // このテストが、testInJMockitWithMockups() の後に実行されると
  // モックしていないCalcを使っているつもりがモックされたものになってしまう様子。
  @Test
  public void testAsUsual() throws Exception {
    Logic logic = new Logic(new Calc());
    int[] result = logic.getDivisibleNumbers();
    assertTrue(result[0] % result[1] == 0);
  }


  @Test
  public void testInJMockitWithMockups() throws Exception {
    new MockUp<Calc>() {
      @Mock()
      public int remainder(int dividend, int divisor) {
        return divisor == 5 ? 0 : 1;
      }
    };
    Logic logic = new Logic(new Calc());
    int[] result = logic.getDivisibleNumbers();
    assertTrue(result[1] == 5);
  }
}

LogicTestInMockito.java

package org.example;

import org.junit.Before;
import org.junit.Test;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;

import static org.junit.Assert.assertTrue;
import static org.mockito.Mockito.anyInt;
import static org.mockito.Mockito.when;

public class LogicTestInMockito {

  @Mock
  Calc calc;

  @InjectMocks
  Logic logic;

  @Before
  public void before() {
    MockitoAnnotations.initMocks(this);
  }

  @Test
  public void testAsUsual() throws Exception {
    logic.calc = new Calc();
    int[] result = logic.getDivisibleNumbers();
    assertTrue(result[0] % result[1] == 0);
  }

  @Test
  public void testInMockito() throws Exception {
    when(calc.remainder(anyInt(), anyInt())).thenAnswer(i -> {
      // 公式ドキュメントには書いてありませんが、ここはラムダが使えます。
      return ((Integer) i.getArguments()[1]) == 5 ? 0 : 1;
    });
    int[] result = logic.getDivisibleNumbers();
    assertTrue(result[1] == 5);
  }
}