CODEWITHSUNDEEP
javaunit-testingmockito
Josh J
Josh J

Reputation: 6893

Mockito @Mock does not inject named mocks correctly using constructor injection

I am trying to use @Mock to inject two different objects into my class under test. I need them to be two different objects so that I can use when on each one to produce different results. Everything I've searched on SO points toward this working, but when running the test below - both objects are the same mock.

import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.when;

import com.ihm.pp.test.UnitTest;
import org.junit.Test;
import org.junit.experimental.categories.Category;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.junit.MockitoJUnitRunner;

/**
 * @author Josh Johnston
 */
@Category(UnitTest.class)
@RunWith(MockitoJUnitRunner.class)
public class ConstructorInjectionBug {

  @Mock
  private IBroken aBroken;

  @Mock
  private IBroken bBroken;

  @InjectMocks
  private UsesBroken usesBroken;

  @Test
  public void testBrokenConstructorInjection() {

    when(bBroken.getNumber()).thenReturn(2);
    assertEquals(2, usesBroken.getbBroken().getNumber());

    when(aBroken.getNumber()).thenReturn(1);
    assertEquals(1, usesBroken.getaBroken().getNumber());
  }
}

interface IBroken {
  int getNumber();
}

class UsesBroken {

  private IBroken aBroken;
  private IBroken bBroken;

  public UsesBroken(IBroken aBroken, IBroken bBroken) {
    this.aBroken = aBroken;
    this.bBroken = bBroken;
  }

  public IBroken getaBroken() {
    return aBroken;
  }

  public IBroken getbBroken() {
    return bBroken;
  }
}

Result:

java.lang.AssertionError:
    Expected :1
    Actual   :2

at org.junit.Assert.failNotEquals(Assert.java:834)
    at org.junit.Assert.assertEquals(Assert.java:645)
    at org.junit.Assert.assertEquals(Assert.java:631)
    at ConstructorInjectionBug.testBrokenConstructorInjection(ConstructorInjectionBug.java:37)

Upvotes: 5

Views: 2811

Answers (1)

Nkosi
Nkosi

Reputation: 247163

@InjectMocks wont know which IBroken to inject. So it is not that it is broken but more the design is flawed.

You would need to explicitly inject the mocks into the subject under test to get the desired behavior.

@Category(UnitTest.class)
@RunWith(MockitoJUnitRunner.class)
public class ConstructorInjectionBug {

  @Mock
  private IBroken aBroken;

  @Mock
  private IBroken bBroken;

  private UsesBroken usesBroken;

  @Test
  public void testBrokenConstructorInjection() {
    //Arrange
    usesBroken = new UsesBroken(aBroken, bBroken);
    when(bBroken.getNumber()).thenReturn(2);
    when(aBroken.getNumber()).thenReturn(1);

    //Act & Assert
    assertEquals(2, usesBroken.getbBroken().getNumber());    
    assertEquals(1, usesBroken.getaBroken().getNumber());
  }
}

Upvotes: 6

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