Mocked private method with PowerMock, but underlying method still gets called

Question

I am trying to mock out a private method that is making a JNDI call. When that method gets called from a unit test, it throws an exception^. I would like to mock-out that method for testing purposes. I used the sample code from another questions answer, and while the test passes, it seems that the underlying method still gets called. I inserted a System.err.println() in the doTheGamble() method, and it gets printed out to my console.

Interesting enough, if I comment out the first assertThat, the test passes. ?:(

So, how do I mock out a private method so that it does not get called?

import static org.hamcrest.core.Is.is; import static org.junit.Assert.assertThat; import static org.mockito.Matchers.anyInt; import static org.mockito.Matchers.anyString; import static org.powermock.api.mockito.PowerMockito.when; import static org.powermock.api.support.membermodification.MemberMatcher.method;  import java.util.Random;  import org.junit.Test; import org.junit.runner.RunWith; import org.powermock.api.mockito.PowerMockito; import org.powermock.core.classloader.annotations.PrepareForTest; import org.powermock.modules.junit4.PowerMockRunner;  @RunWith(PowerMockRunner.class) @PrepareForTest(CodeWithPrivateMethod.class) public class PowerMock_Test {      static boolean gambleCalled = false;       @Test(expected = RuntimeException.class)     public void when_gambling_is_true_then_always_explode() throws Exception {         CodeWithPrivateMethod spy = PowerMockito.spy(new CodeWithPrivateMethod());          when(spy, method(CodeWithPrivateMethod.class, "doTheGamble", String.class, int.class))                 .withArguments(anyString(), anyInt())                 .thenReturn(true);  /* 1 */ assertThat( PowerMock_Test.gambleCalled, is(false) );         spy.meaningfulPublicApi(); /* 2 */ assertThat( PowerMock_Test.gambleCalled, is(false) );     } }   class CodeWithPrivateMethod {      public void meaningfulPublicApi() {         if (doTheGamble("Whatever", 1 << 3)) {             throw new RuntimeException("boom");         }     }      private boolean doTheGamble(String whatever, int binary) {         Random random = new Random(System.nanoTime());         boolean gamble = random.nextBoolean();          System.err.println( "\n>>> GAMBLE CALLED <<<\n" );         PowerMock_Test.gambleCalled = true;          return gamble;     } }    

^ understandably, since my workspace does not support JNDI, only the production environment does

% I am using the latest versions of all the library, JUnit 4.10, Mockito 1.8.5, Hamcrest 1.1, Javassist 3.15.0, and PowerMock 1.4.10.

Answer 1

From the PowerMock Private Method Example:

@RunWith(PowerMockRunner.class) // We prepare PartialMockClass for test because it's final or we need to mock private or static methods @PrepareForTest(PartialMockClass.class) public class YourTestCase { @Test public void privatePartialMockingWithPowerMock() {             PartialMockClass classUnderTest = PowerMockito.spy(new PartialMockClass());      // use PowerMockito to set up your expectation     PowerMockito.doReturn(value).when(classUnderTest, "methodToMock", "parameter1");      // execute your test     classUnderTest.execute();      // Use PowerMockito.verify() to verify result     PowerMockito.verifyPrivate(classUnderTest, times(2)).invoke("methodToMock", "parameter1"); } 

So to apply this to your code, I think it might become:

@RunWith(PowerMockRunner.class) @PrepareForTest(CodeWithPrivateMethod.class) public class PowerMock_Test {     @Test(expected = RuntimeException.class)     public void when_gambling_is_true_then_always_explode() throws Exception {         CodeWithPrivateMethod spy = PowerMockito.spy(new CodeWithPrivateMethod());          PowerMockito.doReturn(true).when(spy, "doTheGamble", anyString(), anyInt());   /* 1 */ PowerMockito.verifyPrivate(spy, times(0)).invoke("doTheGamble", anyString(), anyInt());                     spy.meaningfulPublicApi(); /* 2 */ PowerMockito.verifyPrivate(spy, times(2)).invoke("doTheGamble", anyString(), anyInt());                 } } 

I just coded that in the editor here. No tests have actually been run, and no bugs have been harmed in the crafting of this code.

Answer 2

ArtB,

Just pasting the complete code which works fine in my Eclipse IDE. I have only changed the expectation i said in my last post. Good luck.

import static org.hamcrest.core.Is.is; import static org.junit.Assert.assertThat; import static org.mockito.Matchers.anyInt; import static org.mockito.Matchers.anyString; import static org.powermock.api.support.membermodification.MemberMatcher.method;  import java.util.Random;  import org.junit.Test; import org.junit.runner.RunWith; import org.powermock.api.mockito.PowerMockito; import org.powermock.core.classloader.annotations.PrepareForTest; import org.powermock.modules.junit4.PowerMockRunner;  @RunWith(PowerMockRunner.class) @PrepareForTest(CodeWithPrivateMethod.class) public class PowerMock_Test {      static boolean gambleCalled = false;       @Test(expected = RuntimeException.class)     public void when_gambling_is_true_then_always_explode() throws Exception {         CodeWithPrivateMethod spy = PowerMockito.spy(new CodeWithPrivateMethod());  //        PowerMockito.doReturn(true).when(spy, "doTheGamble", anyString(), anyInt());          PowerMockito.doReturn(true).when(spy,                 method(CodeWithPrivateMethod.class, "doTheGamble", String.class, int.class))                 .withArguments(anyString(), anyInt());          assertThat( PowerMock_Test.gambleCalled, is(false) );         spy.meaningfulPublicApi();         assertThat( PowerMock_Test.gambleCalled, is(false) );     } }   class CodeWithPrivateMethod {      public void meaningfulPublicApi() {         if (doTheGamble("Whatever", 1 << 3)) {             throw new RuntimeException("boom");         }     }      private boolean doTheGamble(String whatever, int binary) {         Random random = new Random(System.nanoTime());         boolean gamble = random.nextBoolean();          System.err.println( "\n>>> GAMBLE CALLED <<<\n" );         PowerMock_Test.gambleCalled = true;          return gamble;     } }