public B mock(String mock) {
        this.mock = mock;
        return getThis();
    }
@Test
    void mock() {
        MethodBuilder builder = new MethodBuilder();
        builder.mock("mock");
        Assertions.assertEquals("mock", builder.build().getMock());
        builder.mock("return null");
        Assertions.assertEquals("return null", builder.build().getMock());
    }