How to properly mock data object for unit tests? - node.js

Question

I'm trying to unit test a chunk of code that looks something like the snippet below.
const getSubscriptions = {
options: {
async handler({query}) {
const workType = searchParams.get('workType');
return axios.get(url, {
headers: {
Authorization: `Bearer ${clientCredentials.access_token}`
}
}).then((response) => {
if (workType && workType.length > 0) {
if (workType === 'Unknown') {
response.data._embedded = response.data._embedded.filter((subscriptions) => !subscriptions.systemProperties.workType);
} else {
response.data._embedded = response.data._embedded.filter((subscriptions) => subscriptions.systemProperties.workType && subscriptions.systemProperties.workType === workType);
}
}
return response.data;
})
}
},
method: 'GET',
path: '/subscriptions'};
I'm seeing errors such as "cannot read property 'filter' of undefined" in the existing tests after adding the .filter usage. How can I properly mock this in my unit tests so that filter is recognized as a function? Currently the tests are passing in a data object that looks like:
data: [chance.object(), chance.object()]
I've tried editing this data object to include _embedded and then I get an error that .filter is not a function.
I'm new to writing unit tests for JavaScript, so I've been stuck on this for a while. Any help is appreciated. I'm using Mocha for testing, but can likely interpret a Jasmine or Jest solution as well.
Here is a trimmed down version of the test suite:
describe('Get subscriptions', () => {
const workType = chance.word();
const getSubscriptionsResponse = {
data: [chance.object(), chance.object()]
};
const expectedRequest = {
auth: {
...expectedAuth
},
path: '/subscriptions',
query: {
workType
}
};
it('should call API with auth token for Subscriptions', async () => {
const axiosStub = sinon.stub(axios, 'get').resolves(getSubscriptionsResponse);
const expectedParams = new URLSearchParams(expectedRequest.query);
await getSubscriptionsRoute.options.handler(expectedRequest);
expect(axiosStub).to.have.callCount(1);
expect(axiosStub).to.be.calledWith(expectedUrl, {
headers: {
Authorization: `${accessToken}`
}
});
});

Answer 1

The code is trying to filter the response.data._embedded array — response.data is an object. You should mock the response data to be an object (with the _embedded property) and not an array.
{
data: [chance.object(), chance.object()]
}
should be
{
data: {
_embedded: [
// ...
]
}
}