How to get request's body with fetch-mock

Question

I have tests which use fetch-mock to mock a post request with parameters in the body.

I can mock the request but i cannot find a way to return a response according to the request's body.

Lets say i have a post request with :

const body = {flag : true} // can be either true or false
const configInit: RequestInit = {
        method: "POST",
        credentials: "include",
        body: JSON.stringify(body)
    };

fetch(REQUEST_URL, configInit)

Currently my mock looks like this:

//.. some definithion of responseA and responseB 
fetchMock.post(
                REQUEST_URL,
                (url, opts) =>  opts && opts.body && opts.body.flag ? responseA : responseB ,
                { overwriteRoutes: true }
);

But it says that opts.body is a 'BodyInit' object and does not have property "flag".

I have found the docomentation but i couldn't find anywhere the right way of doing this. How can i get the parameters from the request to my mock response? Is this way the best practice? maybe i should separate the requests using a FunctionMatcher (which doesn't work for me either)?

Answer 1

I'm not sure of best pattern or anything but my quick solution is just to call the toString() method that BodyInit provides so for example:

fetchMock.get('someUrl', (_, opts) => {
  const body = JSON.parse(opts.body.toString())
})

Sorry for the incomplete answer just enough to hopefully get you on your way