Java – robolectric shadow does not work

I tried to create a test with robolectric My goal is to be able to replace the functionality of a class from custom behavior (for example, from a library without modifying the code)

I created this little test to simulate what I want to do:

@RunWith(RobolectricTestRunner.class)
@Config(shadows = {ShadowMessenger.class})
public class TestShadow {

    @Test
    public void testMessenger() {
        OriginalMessenger messenger = new OriginalMessenger();
        String message = messenger.getMessage();
        Assert.assertEquals("Shadow messenger",message);
    }

    public static class OriginalMessenger {

        public String getMessage() {
            return "Original messenger";
        }
    }

    @Implements(OriginalMessenger.class)
    public static class ShadowMessenger extends OriginalMessenger {

        @Implementation
        public String getMessage() {
            return "Shadow messenger";
        }
    }
}

In this example, originalmessanger is a class in the library and provides default functionality Shadowmessenger is a class that contains custom behavior to apply when I use original messenger

But when I failed to run the test The content of the message is "original messenger" It seems that shadowmessenger has never been used

What on earth did I do wrong?

Solution

So you can only shadow Android classes However, you can also influence your course by testing runners with a customized robolectric

Robolectric 3.1. 4 (robolectricgradletestrunner has been completely deleted, so you need to override the method described in robolectrictestrunner)

@Override
protected ShadowMap createShadowMap() {
    return new ShadowMap.Builder()
        .addShadowClass(OriginalMessenger.class,ShadowMessenger.class,true,true)
        .build();
}

Robolectric 3.0

@Override
public InstrumentationConfiguration createClassLoaderConfig() {
    InstrumentationConfiguration.Builder builder = InstrumentationConfiguration.newBuilder();
    builder.addInstrumentedClass(OriginalMessenger.class.getName());
    return builder.build();
}

Robolectric 2.4

@Override
protected ClassLoader createRobolectricClassLoader(Setup setup,SdkConfig sdkConfig) {
    return super.createRobolectricClassLoader(new ExtraShadows(setup),sdkConfig);
}

class ExtraShadows extends Setup {
    private Setup setup;

    public ExtraShadows(Setup setup) {
        this.setup = setup;
    }

    public boolean shouldInstrument(ClassInfo classInfo) {
        boolean shoudInstrument = setup.shouldInstrument(classInfo);
        return shoudInstrument
                || classInfo.getName().equals(OriginalMessenger.class.getName());
    }
}

Sample project https://github.com/nenick/android-gradle-template/