Add mockResolvedValue, mockResolvedValueOnce, mockRejectedValue, mock…

…RejectedValueOnce to jest mocked functions

definitions/npm/jest_v22.x.x/flow_v0.39.x-/jest_v22.x.x.js

@@ -1,3 +1,9 @@
+type ExtractPromiseValueFunc = <Value>(Promise<Value>) => Value;
+type ExtractPromiseValue<PromiseValue> = $Call<
+  ExtractPromiseValueFunc,
+  PromiseValue
+>;
+
 type JestMockFn<TArguments: $ReadOnlyArray<*>, TReturn> = {
   (...args: TArguments): TReturn,
   /**
@@ -63,7 +69,24 @@ type JestMockFn<TArguments: $ReadOnlyArray<*>, TReturn> = {
   /**
    * Sugar for only returning a value once inside your mock
    */
-  mockReturnValueOnce(value: TReturn): JestMockFn<TArguments, TReturn>
+  mockReturnValueOnce(value: TReturn): JestMockFn<TArguments, TReturn>,
+
+  /**
+   * Sugar functions for returning a resolved Promise (Jest v22.2+)
+   */
+  mockResolvedValue(
+    value: ExtractPromiseValue<TReturn>
+  ): JestMockFn<TArguments, TReturn>,
+
+  mockResolvedValueOnce(
+    value: ExtractPromiseValue<TReturn>
+  ): JestMockFn<TArguments, TReturn>,
+
+  /**
+   * Sugar functions for returning a rejected Promise (Jest v22.2+)
+   */
+  mockRejectedValue(value: any): JestMockFn<TArguments, TReturn>,
+  mockRejectedValueOnce(value: any): JestMockFn<TArguments, TReturn>
 };
 
 type JestAsymmetricEqualityType = {

definitions/npm/jest_v22.x.x/flow_v0.39.x-/test_jest-v22.x.x.js

@@ -13,12 +13,16 @@ jest.atoMockOff();
 const mockFn = jest.fn();
 mockFn.mock.calls.map(String).map(a => a + a);
 
-type Foo = {
-  doStuff: string => number
-};
+type Foo = {|
+  doStuff: string => number,
+  doAsyncStuff: void => Promise<number>
+|};
 const foo: Foo = {
   doStuff(str: string): number {
     return 5;
+  },
+  doAsyncStuff(): Promise<number> {
+    return Promise.resolve(5);
   }
 };
 foo.doStuff = jest.fn().mockImplementation(str => 10);
@@ -44,6 +48,28 @@ foo.doStuff = jest.fn().mockReturnValueOnce(10);
 // $ExpectError Mock function expected to return number, not string.
 foo.doStuff = jest.fn().mockReturnValueOnce("10");
 
+foo.doAsyncStuff = jest.fn().mockResolvedValue(10);
+// $ExpectError Mock function expected to return Promise<number>, not Promise<string>.
+foo.doAsyncStuff = jest.fn().mockResolvedValue("10");
+// $ExpectError Can't return a Promise from a non async function
+foo.doStuff = jest.fn().mockResolvedValue(10);
+
+foo.doAsyncStuff = jest.fn().mockResolvedValueOnce(10);
+// $ExpectError Mock function expected to return Promise<number>, not Promise<string>.
+foo.doAsyncStuff = jest.fn().mockResolvedValueOnce("10");
+// $ExpectError Can't return a Promise from a non async function
+foo.doStuff = jest.fn().mockResolvedValueOnce(10);
+
+foo.doAsyncStuff = jest.fn().mockRejectedValue(new Error("error"));
+// NOTE: No error as Flow doesn't type rejections
+foo.doAsyncStuff = jest.fn().mockRejectedValue("10");
+
+foo.doAsyncStuff = jest.fn().mockRejectedValueOnce(new Error("error"));
+// NOTE: No error as Flow doesn't type rejections
+foo.doAsyncStuff = jest.fn().mockRejectedValueOnce("10");
+
+
+
 const mockedDoStuff = (foo.doStuff = jest.fn().mockImplementation(str => 10));
 mockedDoStuff.mock.calls[0][0].indexOf("a");
 // $ExpectError function `doesntExist` not found in string.