Testing async methods in jest gets mock resolved values mixed up-CodePudding

I'm writing some jest tests to test an async method. If I run each test individually, it works! However, when I run the whole suite, they fail. The mock values from one test end up in another test because I suspect that jest is not waiting for one to finish before moving onto another.

describe('testing method', () => {
test('test case 1', async () => {
dependentService.method.mockResolvedValueOnce(mockResult1);
expect(await testSubject(input)).toBe(expectedResult);
});
 test('test case 2', async () => {
dependentService.method.mockResolvedValueOnce(mockResult2);
expect(await testSubject(input)).toBe(expectedResult);
});
});

In the above sample code snippet, the mockResult2 is used in the test case 1, instead of mockResult1. How do I get this to behave as I expect?

CodePudding user response：

Changing up the expect syntax will solve the problem.

await expect(testSubject(input)).resolves.toBe(expectedResult)

The toBe part of that line is mandatory - without it jest wont wait for the promise to resolve and the framework will mix up promises across tests.

CodePudding user response：

Jest executes all testcases in parallel but you can execute serially by adding this flag

jest --runInBand