How to mock a module that is required in another module with Jasmine

Question

const Client = require('./src/http/client');

module.exports.handler = () => {
    const client = new Client();
    const locationId = client.getLocationId(123);
};

How can I test this module asserting that the client.getLocationId has been called with the 123 argument in Jasmine?

I know how to achieve that with Sinon, but I have no clue about Jasmine.

Answer 1

Where with Sinon you would do:

Sinon.spy(client, 'getLocationId');

...

Sinon.assert.calledWith(client.getLocationId, 123);

with Jasmine you do:

spyOn(client, 'getLocationId');

...

expect(client.getLocationId).toHaveBeenCalledWith(123);

---

Update: So, what you need is to mock the Client module when it's required by the module you're testing. I suggest using Proxyquire for this:

const proxyquire = require('proxyquire');
const mockedClientInstance = {
  getLocationId: () => {}
};
const mockedClientConstructor = function() {
  return mockedClientInstance;
};

const moduleToTest = proxyquire('moduleToTest.js', {
  './src/http/client': mockedClientConstructor
});

This will inject your mock as a dependency so that when the module you're testing requires ./src/http/client, it will get your mock instead of the real Client module. After this you just spy on the method in mockedClientInstance as normal:

spyOn(mockedClientInstance, 'getLocationId');
moduleToTest.handler();
expect(mockedClientInstance.getLocationId).toHaveBeenCalledWith(123);