@angular/core/testinglink

Fixture for debugging and testing a component.

An abstract class for inserting the root test component element in a platform independent way.

把一个测试函数包装进一个异步测试区域（Zone）。当该区域中的所有异步调用都已完成时，该测试将会自动完成。 可用于包装 inject调用。

Wraps a test function in an asynchronous test zone. The test will automatically complete when all asynchronous calls within this zone are done. Can be used to wrap an injectcall.

Discard all remaining periodic tasks.

Wraps a function to be executed in the fakeAsync zone:

• microtasks are manually executed by calling flushMicrotasks(),
• timers are synchronous, tick() simulates the asynchronous passage of time.

Simulates the asynchronous passage of time for the timers in the fakeAsync zone by draining the macrotask queue until it is empty. The returned value is the milliseconds of time that would have been elapsed.

Flush any pending microtasks.

Allows injecting dependencies in beforeEach() and it().

Clears out the shared fake async zone for a test. To be called in a global beforeEach.

Simulates the asynchronous passage of time for the timers in the fakeAsync zone.

Configures and initializes environment for unit testing and provides methods for creating components and services in unit tests.

Static methods implemented by the TestBedViewEngine and TestBedRender3

Type used for modifications to metadata

Returns a singleton of the applicable TestBed.