Adding a ^ to the beginning of a string means a url must begin with the rest of the string. e.g.
fetchMock.mock('^http://example.com', 200);
Will match http://example.com, http://example.com/thing.html etc.
If mocking lots of routes you can name them
fetchMock({
name: 'example',
matcher: 'http://example.com.thing.html'
response: 200
})
Since version 4.5.4 a bug's been fixed, meaning your tests should run in environments where fetch doesn't exist as a global in the test environment, though is assumed to in production. There shouldn't be any need to use the deprecated useNonGlobalFetch() method ever either
To delay responses you can wrap the response in a Promise
fetchMock.mock('^http://example.com', new Promise(res => setTimeout(res, 200)).then(() => 200));
For test involving complex asynchronous interactions use functions that return Promises
fetchMock.mock('^http://example.com', (url, opts) => {
return opts.headers.Auth ? callApi().then(200) : 403
});
By default any unmatched calls go straight through to fetch. Set fetchMock.greed = 'bad' to make them all error, or fetchMock.greed = 'good' to return 200 responses
When using webpack and it's variety of plugins alongside karma, fetch-mock, isomorphic fetch and others sometimes the easiest way to define fetch in the environment is to include it as a standalone script (npm install whatwg-fetch) and leave it out of your main bundle. Or run your tests in firefox/chrome, where fetch is native