Learning Node.js Development

Swapping of the function with spy

For our purposes, we need a spy so we can simulate that function inside of app.js (saveUser). We need a way to replace saveUser function with a spy. Then we can verify that when handleSignup gets called, it does indeed call saveUser. It doesn't need to actually go through the process over in db.js; this is not important to our tests. The only thing that is important is that the function was called with the correct arguments.

To do that, we'll look at an npm module called rewire, which lets us swap out variables for our tests. In our case, in our test file, we'll be able to replace the db object with something else completely. Then, when the code runs, instead of calling db.saveUser as defined in app.js, it ...