node.js - Cannot handle exceptions generated by require() in jest.isolatemodule()

Question

This is the code I want to test:

mongoose
    .connect(dbUrl, { useNewUrlParser: true })
    .then(({ connection }) => {
        console.info(`Main database connected to ${connection.host} on port ${connection.port}`);
    })
    .catch((error) => {
        throw new Error(`Main database connection error: ${error}`);
    });

For some reasons, I need to intercept the error when the module is required. So I mocked mongoose and wrote my test (simplified):

const run = async () => {
    let App;

    try {
        jest.isolateModules(() => {
            App = require('@App/index');
        });
        
    } catch (_e) {
        return true;
    }
};

it('throws error if db connection fails', async () => {
    mongoose.connect.mockImplementation(() => Promise.reject());

    const error = await run();

    expect(error).toBeTruthy();
});

All my tests runs well, except for those that should intercepts unhandled errors

I tried:

• intercept the exception with process.on('uncaughtException', /.../) and unhandledRejection
• use a try catch block around require('@App/index')
• Override Promise.prototype.catch (I was desperate)

I think jest.isolateModules creates some kind of isolated environment where I cannot access/modify, but I cannot understand how I can change this behavior

question from:https://stackoverflow.com/questions/66048332/cannot-handle-exceptions-generated-by-require-in-jest-isolatemodule

Answer 1

Waitting for answers