Jest mockResolvedValue不适用于Typescript中的数组

我们这里有一个令人费解的问题。为什么Jest mockResolvedValue不能模拟数组的解析值。相同的值在mockImplementation中起作用。

export interface Car {
    name: string;
    key: string;
    count?: number;
}

async getCars(): Promise<Car[]> {
    const results = await someLongCall()   // async call
    const c: Car[] = [...results];  // return is of type Car[]
    return c;
}

在我们的测试中

const c: Car[] = [
 {name: 'aaaaa', key: 'aaaaa', count: 10}, 
 {name: 'bbbbb', key: 'bbbbb', count: 20}
 ];

// this fails
_wSpy1 = jest.spyOn(CarSevice.prototype, 'getCars')
      .mockResolvedValue(c);  <= Error here ?


// but this works
_wSpy1 = jest.spyOn(CarSevice.prototype, 'getCars')
   .mockImplementation(() => Promise.resolve(c));

我们得到的错误是:

// We get this error:

Error: Argument of type 'Car[]' is not assignable to parameter of 
type 'Promise<Car[]> | PromiseLike<Promise<Car[]>>'.
Property 'then' is missing in type 'Car[]' but required in type
'PromiseLike<Promise<Car[]>>'. 
[2345] lib.es5.d.ts(1383, 5): 'then' is declared here.

mockResolvedValue的签名如下。值不能不在类型数组上吗?

/**
 * Simple sugar function for: `jest.fn().mockImplementation(() =>
    Promise.resolve(value));`
 */
mockResolvedValue(value: T | PromiseLike<T>): Mock<Promise<T>, Y>;