add assignability tests

packages/jest-mock/__typetests__/Mocked.test.ts

@@ -46,20 +46,22 @@ expectType<[a: string, b?: number]>(
   MockSomeClass.prototype.methodB.mock.calls[0],
 );
 
-const mockExample = new MockSomeClass('c') as Mocked<
+const mockSomeInstance = new MockSomeClass('a') as Mocked<
   InstanceType<typeof MockSomeClass>
 >;
 
-expectType<[]>(mockExample.methodA.mock.calls[0]);
-expectType<[a: string, b?: number]>(mockExample.methodB.mock.calls[0]);
+expectType<[]>(mockSomeInstance.methodA.mock.calls[0]);
+expectType<[a: string, b?: number]>(mockSomeInstance.methodB.mock.calls[0]);
 
-expectError(mockExample.methodA.mockReturnValue('true'));
+expectError(mockSomeInstance.methodA.mockReturnValue('true'));
 expectError(
-  mockExample.methodB.mockImplementation((a: string, b?: string) => {
+  mockSomeInstance.methodB.mockImplementation((a: string, b?: string) => {
     return;
   }),
 );
 
+expectAssignable<SomeClass>(mockSomeInstance);
+
 // mocks function
 
 function someFunction(a: string, b?: number): boolean {
@@ -73,6 +75,8 @@ expectType<[a: string, b?: number]>(mockFunction.mock.calls[0]);
 expectError(mockFunction.mockReturnValue(123));
 expectError(mockFunction.mockImplementation((a: boolean, b?: number) => true));
 
+expectAssignable<typeof someFunction>(mockFunction);
+
 // mocks async function
 
 async function someAsyncFunction(a: Array<boolean>): Promise<string> {
@@ -90,6 +94,8 @@ expectError(
   ),
 );
 
+expectAssignable<typeof someAsyncFunction>(mockAsyncFunction);
+
 // mocks function object
 
 interface SomeFunctionObject {
@@ -124,6 +130,8 @@ expectError(
   }),
 );
 
+expectAssignable<SomeFunctionObject>(mockFunctionObject);
+
 // mocks object
 
 const mockConsole = console as Mocked<typeof console>;