Building Effective Unit Tests

error.txt

java.lang.RuntimeException: Method getString in android.content.Context not mocked. See https://sites.google.com/a/android.com/tools/tech-docs/unit-testing-support for details.
	at android.content.Context.getString(Context.java)

instrumented_build.gradle

dependencies {
    androidTestCompile 'com.android.support.test:runner:0.3'
    androidTestCompile 'com.android.support.test:rules:0.3'
}

MockExampleTest.java

@RunWith(MockitoJUnitRunner.class)
public class MockExampleTest {

    @Mock
    Context mockContext;

    @Test
    public void readStringFromContext() {
        when(mockContext.getString(R.string.app_name)).thenReturn("GDG2015");

        ReadData readdata = new ReadData(mockContext);
        String actualResult = readdata.getAppName();
        assertEquals("GDG2015", actualResult);
    }
}

ReadDataFromContext.java

@RunWith(AndroidJUnit4.class)
public class ReadDataFromContext {

    @Test
    public void readAppNameFromStringResource() {
        ReadData readData = new ReadData(InstrumentationRegistry.getTargetContext());
        assertEquals("GDG2015", readData.getAppName());
    }

}

runner_build.gradle

android {
    defaultConfig {
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
}

unit_build.gradle

dependencies {
    testCompile 'junit:junit:4.12'
    testCompile 'org.mockito:mockito-core:1.10.19'
    androidTestCompile 'org.hamcrest:hamcrest-library:1.1'
}