Save API responses for testing.
const httpSaver = new HttpSaver()
Deno.test('some API', () => {
using _ = httpSaver.stubFetch()
// First time the test runs, the response will be saved under `_fixtures/responses`
// Subsequent test runs will use the saved response, without making a network request
const res = await fetch('https://api.example.com')
// ... do something with `res`
})