[Bug]: Test Suite Fail with `jest.isolateModules` when upgrading to 27.4.5

Version

27.4.5

Steps to reproduce

This code snippet

foo.ts
const deploymentLoggers: Logger[] = [];

export const createDeploymentLogger = async (request: DeploymentLoggerArgs): Promise<Logger> => {
    ...
    deploymentLoggers.push(logger);
    return logger;
};

const closeLogger = async (logger: Logger) => {
    const closeDynamoTransports = logger.transports
        .filter(transport => transport instanceof WinstonDynamoDB)
        .map(transport => new Promise<void>(resolve => (transport as WinstonDynamoDB).kthxbye(() => resolve())));

    const closeCloudwatchTransports = flushCloudwatchTransport(logger);

    await Promise.all([...closeDynamoTransports, closeCloudwatchTransports]);
    logger.close();
};

export const closeAllDeploymentLoggers = async () => {
    const promises = [];
    while (deploymentLoggers.length) {
        const logger = deploymentLoggers.pop();
        promises.push(closeLogger(logger));
    }
    await Promise.all(promises);
};

foo.spec.ts
describe('closeAllDeploymentLoggers', () => {
    let cloudwatchTransportSpy;
    let flushCloudwatchTransportSpy;
    let createDeploymentLogger
    let loggers;
    beforeEach(() => {
        jest.isolateModules(() => {
            ({ closeAllDeploymentLoggers, createDeploymentLogger } = require('foo'));
        });
    });

    beforeEach(async () => {
        flushCloudwatchTransportSpy = jest.spyOn(CloudwatchLogger, 'flushCloudwatchTransport').mockResolvedValue(undefined);
        loggers = [];
        loggers.push(await createDeploymentLogger(loggerParams));
        loggers.push(await createDeploymentLogger({ ...loggerParams, logStreamName: 'le-log-stream-2' }));

        await closeAllDeploymentLoggers();
    });

    it('should flush cloudwatch logs of all loggers', () => {
        expect(flushCloudwatchTransportSpy).toHaveBeenCalledTimes(loggers.length);
    });
});

When running this test i’m getting

Error: expect(jest.fn()).toHaveBeenCalledTimes(expected)

Expected number of calls: 2
Received number of calls: 0

it seems when using jest.isolateModules it “detach” from the last run and not counting the calls in the new version of jest, unlike the previous version where jest count those calls.

The reason we use jest.isolateModules is to reset the deploymentLoggers variable so we need to reimport the package each time, when we change to jest.mock in order to mock the deploymentLoggers and reset it each time the test pass, but i need to jest.requireActual the reset of the module…

this is a breaking change in the way jest.isolateModules works

Expected behavior

It should work in the new version (jest 27.4.5 with ts-jest 27.1.1) as it works in jest version 26.6.3 with ts-jest 26.5.6

Actual behavior

Jest not counting the spyOn calls when using isolateModules

Additional context

No response

Environment

System:
  OS: macOS 12.0.1
  CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Binaries:
  Node: 14.17.0 - ~/.nvm/versions/node/v14.17.0/bin/node
  Yarn: 6.7.6 - /usr/local/bin/yarn
  npm: 6.14.13 - ~/.nvm/versions/node/v14.17.0/bin/npm

[SimenB]

It should work in the new version (jest 27.4.5 with ts-jest 27.1.1) as it works in jest version 26.6.3 with ts-jest 26.5.6

Why? All I’m seeing in this bug report is “my test is now failing”, I don’t see how Jest’s current behaviour is incorrect. I assume the change you’re hitting is https://github.com/facebook/jest/pull/10963, which is definitely a bug fix - isolateModules should return a fresh instance of a module, not the old one.

Can you put together a minimal example (e.g. without typescript, and preferably just a minimal file and minimal test) for us to look at, that passes with v26 and fails with v27? Easier to judge if the behaviour should be considered a bug or not then. 🙂

[yaronya]

Just import the logger inside the same isolateModules and mock it there

This might be a workaround, but I believe it’s legitimate to expect the library to not fail on those scenarios.

Either way, this is not a bug in v27, so closing this.

I strongly disagree here. I’ve upgraded to v27 from v26 and things started failing w/o any code change. I don’t know how to call it other than “bug”…