Collecting Coverage Reports in Jest with Integration Tests - express

Question

I have a bunch of tests setup with Jest that test Express server endpoints in the same repo. In order to accomplish this testing, I have Jest spinning up an Express server in the beforeAll() method. When I run Jest with the --coverage flag, I get coverage information for just the scripts that were run in order to start Jest and no reporting on the scripts that were triggered by hitting the endpoints. That makes sense, but is there a way to get coverage information on the endpoint code?
Snippet of test code:
const rp = require('request-promise')
describe('testFunctions', () => {
beforeAll(done => {
app.listen(config.PORT, async () => {
done()
})
})
it('hit endpoint', async () => {
const response = await rp({ uri: '/testFunctions', method: 'POST' })
expect(response).toEqual('response)
})
})
I'm trying to get a coverage report for all of the server code hit with the /testFunctions request.

Answer 1

This is the solution that worked for me. It required a bit of refactoring, but I think it was cleaner in the end. In my ecosystem, we are running a Parse Server as middleware with an Express server, but this could apply to anyone who needs to run a separate server with the tests.
So to get my server in a place that nyc (the coverage reporting tool I'm using) could monitor, I abstracted the server initialization completely out of the jest test suite and created a special npm script to run it in an entirely separate process.
NPM Script (package.json):
"scripts": {
"coverage": "nyc --silent npm start & ./listen_on_port_5000.sh && jest test/cloud/integration && kill $(lsof -t -i tcp:5000) && nyc report --reporter=html",
}
listen_on_port_5000.sh
while ! nc -z localhost 5000
do
sleep 0.5
done
So how does this work?
nyc --silent npm start runs which is the normal command we would run to start our server with Express and Parse but with the prepended nyc part with the --silent flag so that nyc can run in the background and watch the server code.
Because we know that the server always starts on port 5000, we run the start script in the background and start a separate process running a shell script (listen_on_port_5000.sh) to wait for the server to boot up.
Once the listener script detects anything running on port 5000, the npm script moves onto the jest command (all while the Express server is up and running).
When Jest finishes running, the final script runs a kill script to close the server running on port 5000.
We then run a second nyc script to generate the report that it collected in the first script. The generated report can be found in your project's directory under /coverage/lcov-report/ (or you can use a different coverage reporter.