SystemUnderTestFactoryTester.java

SystemUnderTestFactoryTester.java

package com.jnericks.testutils;

import org.junit.*;

import java.util.function.*;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.StrictAssertions.assertThatThrownBy;
import static org.mockito.Mockito.*;

public class SystemUnderTestFactoryTester extends BaseUnitTester
{
    SystemUnderTestFactory<System> sutFactory;

    @Before
    public void before()
    {
        sutFactory = new SystemUnderTestFactory<System>() { };
    }

    @Test
    public void should_be_able_to_create_sut()
    {
        System sut = sutFactory.sut();

        assertThat(sut).isExactlyInstanceOf(System.class);
    }

    @Test
    public void should_have_sut_be_a_singleton()
    {
        System sut1 = sutFactory.sut();
        System sut2 = sutFactory.sut();

        assertThat(sut1).isSameAs(sut2);
    }

    @Test
    public void should_have_dependency_a()
    {
        DependencyA a = sutFactory.dependency(DependencyA.class);

        assertThat(a).isInstanceOf(DependencyA.class);
    }

    @Test
    public void should_have_dependency_b()
    {
        DependencyB a = sutFactory.dependency(DependencyB.class);

        assertThat(a).isInstanceOf(DependencyB.class);
    }

    @Test
    public void should_be_able_to_do_a_stuff()
    {
        sutFactory.sut().doAStuff();

        verify(sutFactory.dependency(DependencyA.class), Once).aStuff();
    }

    @Test
    public void should_be_able_to_do_b_stuff()
    {
        sutFactory.sut().doBStuff();

        verify(sutFactory.dependency(DependencyB.class), Once).bStuff();
    }

    @Test
    public void should_be_able_to_stub_a_method()
    {
        Object objectPassedToSut = new Object();
        Object objectReturnedFromDependencyA = new Object();

        when(sutFactory.dependency(DependencyA.class).doSomething(objectPassedToSut))
                .thenReturn(objectReturnedFromDependencyA);

        Object actual = sutFactory.sut().passToDependencyA(objectPassedToSut);
        assertThat(actual).isSameAs(objectReturnedFromDependencyA);
    }

    @Test
    public void should_be_able_to_retrieve_injected_substitute()
    {
        DependencyA myDependencyA = mock(DependencyA.class);
        sutFactory.forDependency(DependencyA.class).use(myDependencyA);

        assertThat(sutFactory.dependency(DependencyA.class)).isSameAs(myDependencyA);
    }

    @Test
    public void should_be_able_to_assert_on_injected_substitute()
    {
        DependencyA myDependencyA = mock(DependencyA.class);
        sutFactory.forDependency(DependencyA.class).use(myDependencyA);
        sutFactory.sut().doAStuff();

        verify(myDependencyA, Once).aStuff();
    }

    @Test
    public void should_throw_exception_when_configuring_an_object_that_is_NOT_a_dependency()
    {
        assertThatThrownBy(() -> sutFactory.forDependency(NotADependency.class).use(mock(NotADependency.class)))
                .isInstanceOf(UnsupportedOperationException.class);
    }

    @Test
    public void should_throw_exception_when_retrieving_object_that_is_NOT_a_dependency()
    {
        assertThatThrownBy(() -> sutFactory.dependency(NotADependency.class))
                .isInstanceOf(UnsupportedOperationException.class);
    }

    @Test
    public void should_throw_exception_when_trying_to_retrieve_sut_from_method()
    {
        assertThatThrownBy(() -> sutFactory.dependency(System.class))
                .isInstanceOf(UnsupportedOperationException.class);
    }

    @Test
    public void should_be_able_to_override_internal_sut_factory()
    {
        System system = mock(System.class);
        sutFactory.createSutUsing(() -> system);
        assertThat(sutFactory.sut()).isSameAs(system);
    }

    @Test
    @SuppressWarnings("unchecked")
    public void should_be_able_to_add_a_pre_processor()
    {
        Runnable runnable = mock(Runnable.class);

        sutFactory.beforeSutCreated(runnable);
        sutFactory.createSut();

        verify(runnable, Once).run();
    }

    @Test
    @SuppressWarnings("unchecked")
    public void should_be_able_to_add_a_post_processor()
    {
        Consumer<System> consumer = mock(Consumer.class);

        sutFactory.afterSutCreated(consumer);
        sutFactory.createSut();

        verify(consumer, Once).accept(sutFactory.sut());
    }

    @Test
    @SuppressWarnings("unchecked")
    public void should_be_able_to_add_pre_and_post_processors_to_custom_sut_creation()
    {
        Runnable runnable = mock(Runnable.class);
        Consumer<System> consumer = mock(Consumer.class);

        sutFactory.beforeSutCreated(runnable);
        sutFactory.afterSutCreated(consumer);

        sutFactory.createSutUsing(() -> new System(null));
        sutFactory.createSut();

        verify(runnable, Once).run();
        verify(consumer, Once).accept(sutFactory.sut());
    }

    @Test
    @SuppressWarnings("unchecked")
    public void should_be_able_to_swap_in_a_concrete_impl_of_a_dependency()
    {
        Object objectPassedIn = new Object();
        Object objectReturned = new Object();

        Runnable runnable = mock(Runnable.class);
        Function<Object, Object> function = mock(Function.class);
        when(function.apply(objectPassedIn)).thenReturn(objectReturned);

        DependencyA impl = new DependencyAImpl(runnable, function);

        sutFactory.forDependency(DependencyA.class).use(impl);

        sutFactory.sut().doAStuff();
        verify(runnable, Once).run();

        Object actual = sutFactory.sut().passToDependencyA(objectPassedIn);
        verify(function, Once).apply(objectPassedIn);
        assertThat(actual).isSameAs(objectReturned);
    }
}