Mocking static methods with Mockito

Question

I\'ve written a factory to produce java.sql.Connection objects:

public class MySQLDatabaseConnectionFactory implements DatabaseConnectionFactory         


        

Answer 1

Use PowerMockito on top of Mockito.

Example code:

@RunWith(PowerMockRunner.class)
@PrepareForTest(DriverManager.class)
public class Mocker {

    @Test
    public void shouldVerifyParameters() throws Exception {

        //given
        PowerMockito.mockStatic(DriverManager.class);
        BDDMockito.given(DriverManager.getConnection(...)).willReturn(...);

        //when
        sut.execute(); // System Under Test (sut)

        //then
        PowerMockito.verifyStatic();
        DriverManager.getConnection(...);

    }

More information:

• Why doesn't Mockito mock static methods?

Answer 2

Observation : When you call static method within a static entity, you need to change the class in @PrepareForTest.

For e.g. :

securityAlgo = MessageDigest.getInstance(SECURITY_ALGORITHM);

For the above code if you need to mock MessageDigest class, use

@PrepareForTest(MessageDigest.class)

While if you have something like below :

public class CustomObjectRule {

    object = DatatypeConverter.printHexBinary(MessageDigest.getInstance(SECURITY_ALGORITHM)
             .digest(message.getBytes(ENCODING)));

}

then, you'd need to prepare the class this code resides in.

@PrepareForTest(CustomObjectRule.class)

And then mock the method :

PowerMockito.mockStatic(MessageDigest.class);
PowerMockito.when(MessageDigest.getInstance(Mockito.anyString()))
      .thenThrow(new RuntimeException());

Answer 3

As mentioned before you can not mock static methods with mockito.

If changing your testing framework is not an option you can do the following:

Create an interface for DriverManager, mock this interface, inject it via some kind of dependency injection and verify on that mock.