Partial mocking example

PartialMockingTest.java

static class Sample {

    int value;

    Sample() {
        this.value = -1;
    }

    Sample(int value) {
        this.value = value;
    }

    int getValue() {
        return this.value;
    }

    boolean method1() {
        return true;
    }

    static void method2() {
        throw new IllegalStateException();
    }
}

@Test
public void test01() {
    final Sample mock = new Sample();
    new Expectations(Sample.class) {{
        mock.getValue(); result = 123;
    }};

    Sample sut1 = new Sample();
    Sample sut2 = new Sample(1);
    assertThat(sut1.getValue(), is(123)); // mocked
    assertThat(sut2.getValue(), is(123)); // mocked
    assertThat(sut2.value, is(1)); // non-mocked
}

@Test
public void test02() {
    final Sample sut1 = new Sample(1);
    new Expectations(sut1) {{
        sut1.getValue(); result = 123;
        Sample.method2();
    }};

    assertThat(sut1.getValue(), is(123)); // mocked
    assertThat(sut1.method1(), is(true)); // non-mocked

    try {
        Sample.method2(); // mocked
    } catch (Throwable e) {
        fail();
    }

    Sample sut2 = new Sample(2);
    assertThat(sut2.getValue(), is(2)); // non-mocked
    assertThat(sut2.method1(), is(true)); // non-mocked
}