express version: 4.17.1
supertest version: 4.0.2

TLDR; There seems to be some sort of inconsistency between express and supertest when handling routes with single quotes. Or I'm missing something trivial.

I have two express routes. I'm escaping parenthesis in the routes with \\ as suggested in the docs.
app.get('/api/hello-one\\(:msg\\)', (req, res) => res.send({ num: 1, msg: req.params.msg }));
app.get('/api/hello-two\\(\':msg\'\\)', (req, res) => res.send({ num: 2, msg: req.params.msg }));

I have two supertest tests (using mocha to run them):

it('should return correct response for hello-one', (done) => {
const app = createExpressApp(null);
console.log(app._router.stack);
request(app).get(`/api/hello-one('foo')`).expect(200).expect({ num: 1, msg: `'foo'`}, done);
});

it('should return correct response for hello-two', (done) => {
const app = createExpressApp(null);
console.log(app._router.stack);
request(app).get(`/api/hello-two('foo')`).expect(200).expect({ num: 2, msg: `foo`}, done);
});

The first test passes as expected.
The second test fails unexpectedly, with an actual status of 404 instead of the expected 200.
But in the browser (using Firefox),
GET http://localhost:<port>/api/hello-one(foo) and
GET http://localhost:<port>/api/hello-two('foo')
both return the correct objects as expected.

What's going on here? Any help is appreciated!