Testing Sections

The SectionsTestHelper provides easy-to-use helper functions to test the output of GroupSectionSpecs and state updates.

To demonstrate the testing functionality, consider the following simple group section with a list of text and an optional image header:

/**
 * Dummy {@link GroupSectionSpec} to illustrate how to test sections.
 */
@GroupSectionSpec
public class VerySimpleGroupSectionSpec {

  @OnCreateInitialState
  protected static void onCreateInitialState(
      SectionContext c,
      StateValue<Integer> extra) {
    extra.set(0);
  }

  @OnCreateChildren
  protected static Children onCreateChildren(
      SectionContext c,
      @State int extra,
      @Prop int numberOfDummy) {
    Children.Builder builder = Children.create();

    if (extra > 0) {
      builder.child(SingleComponentSection.create(c)
          .component(Image.create(c).drawable(new ColorDrawable()).build()));
    }

    for (int i = 0; i < numberOfDummy+extra; i++) {
      builder.child(SingleComponentSection.create(c)
          .component(Text.create(c).text("Lol hi " + i).build())
          .key("key" + i)
          .build());
    }
    return builder.build();
  }

  @OnDataBound
  static void onDataBound(
      SectionContext c,
      @Prop int numberOfDummy,
      @State(canUpdateLazily = true) int extra) {
    VerySimpleGroupSection.lazyUpdateExtra(c, extra - numberOfDummy);
  }

  @OnUpdateState
  static void onUpdateState(
      StateValue<Integer> extra,
      @Param int newExtra) {
    extra.set(newExtra);
  }

  @OnEvent(ClickEvent.class)
  static void onImageClick(
      SectionContext c) {
    VerySimpleGroupSection.onUpdateState(3);
  }
}

Testing Children

The SectionComponentTestHelper helps you test a group section spec's @OnCreateChildren method by returning the children of a section as a list of SubSection:

  @Test
  public void testInitialChildren() throws Exception {

    Section s = mTester.prepare(
        VerySimpleGroupSection.create(mTester.getContext()).numberOfDummy(4).build());

    List<SubSection> subSections = mTester.getChildren(s);

    assertThat(subSections)
        .isEqualTo(
            ImmutableList.of(
                SubSection.of(
                    SingleComponentSection.create(mTester.getContext())
                        .key("key0")
                        .component(Text.create(mTester.getContext()).text("Lol hi 0"))
                        .build()),
                SubSection.of(SingleComponentSection.class),
                SubSection.of(SingleComponentSection.class),
                SubSection.of(SingleComponentSection.class)));
  }

tip

SubSections can either be matched by exact props or by section class and are best used as existence checks.

Testing State

Sometimes, a section's behaviour is based on both external props and internal state. You can change state variables and test new behaviour by performing state updates on the scoped context:

  @Test
  public void testStateUpdate() throws Exception {

    Section s = mTester.prepare(
        VerySimpleGroupSection.create(mTester.getContext()).numberOfDummy(4).build());

    assertThat(mTester.getChildren(s).size()).isEqualTo(4);

    VerySimpleGroupSection.onUpdateState(mTester.getScopedContext(s), 5);

    assertThat(mTester.getChildren(s).size()).isGreaterThan(4);
  }

Testing Events

Sections, which heavily uses the event handling system, and the SectionComponentTestHelper, which has helper methods, both make testing events easier. Simply create an event handler using the scoped context and dispatch your event to execute the event handler:

  @Test
  public void testClickHandler() throws Exception {
    Section s = mTester.prepare(
        VerySimpleGroupSection.create(mTester.getContext()).numberOfDummy(4).build());


    SectionComponentTestHelper.dispatchEvent(
        s,
        VerySimpleGroupSection.onImageClick(mTester.getScopedContext(s)),
        new ClickEvent());

    VerySimpleGroupSection.VerySimpleGroupSectionStateContainerImpl stateContainer =
        mTester.getStateContainer(s);

    assertThat(stateContainer.extra).isEqualTo(3);
  }

Testing Other Lifecycle Methods

Testing other lifecycle methods is as simple as calling the lifecycle method with the section under test and its corresponding scoped context:

  @Test
  public void testDataBound() throws Exception {
    Section<VerySimpleGroupSection> s = mTester.prepare(
        VerySimpleGroupSection.create(mTester.getContext()).numberOfDummy(4).build());

    s.dataBound(mTester.getScopedContext(s), s);

    VerySimpleGroupSection.VerySimpleGroupSectionStateContainerImpl stateContainer =
        mTester.getStateContainer(s);

    assertThat(stateContainer.extra).isEqualTo(-4);
  }

For the full GitHub source of this example, see the VerySimpleGroupSectionSpecTest.

Testing for sections is still basic so, if you run into any missing functionality, raise a GitHub Facebook issue and describe your use case.