TestContainer

An isolated Container for tests.

The Container is a process-wide singleton, which makes it awkward to mock. TestContainer solves that: create one in beforeEach() and it takes over the Container for that test, letting you replace any factory with a stub. reset() in afterEach() puts it back.

Info

A test framework like Jest runs test files in parallel across cores, and the it() blocks within a file serially. So a TestContainer never leaks into a test running in parallel.

@example

beforeEach(async () => {
  container = await TestContainer.create({ mocks: [] }, { factoryTimeoutInMs: 500 });
});

afterEach(async () => {
  await TestContainer.reset();
});

@group

Functions/Container

Index

Constructors

• constructor

Methods

• create
• reset

Constructors

constructor

• TestContainer(): TestContainer

• Returns TestContainer

Methods

staticcreate

• create(subjects: TestContainerSubjects, options?: TestContainerOptions): Promise<Container>

• To take over the Container for one test, replacing the factories you name.

  @example

  await TestContainer.create({
    mocks: [
      { type: MyClass, value: jest.fn() },
      { metadata: { key: 'value' }, type: AnotherClass, value: new AnotherClass() },
    ],
  }, { factoryTimeoutInMs: 500 });

  ---

  Parameters

  • subjects: TestContainerSubjects

    The subjects being mocked.

    • mocks is an array of objects, to override the default factories.
      • Use metadata?: { [key: string]: string } to identify the factory being mocked.
      • Use type: Constructable<T> | string to identify the class being mocked.
      • Use value: T to provide the mocked value.

  • optionaloptions: TestContainerOptions

    Options to configure TestContainer.

    • factoryTimeoutInMs?: number is to override the default container timeout.
    • force?: boolean performs a complete container reset.

  Returns Promise<Container>

staticreset

• reset(): Promise<void>

• To destroy every factory in the Container. Because it destroys the whole Container and not only the mocks, it must always be called in your teardown block - otherwise the next test starts against a Container this test left behind.

  ---

  Returns Promise<void>