A library for supporting recording and replaying HTTP requests when using HttpClient.

Not just yet, gotta make it work better.

Rather than creating a HttpClient manually, your test should use the HttpClientFactory with a provided cassette to represent the context of the test.

This cassette file is a JSON file on disk, which is used to store cached HTTP requests.

You can then use the received HttpClient instance like you would normally:

using (var httpClient = HttpClientFactory.WithCassette("my-test-scenario"))
{
    var request = new HttpRequestMessage(HttpMethod.Get, "http://www.iana.org/domains/reserved");
    var response = await httpClient.SendAsync(request);
    var body = await response.Content.ReadAsStringAsync();
    body.ShouldContain("Example domains");
}

VCR supports a number of modes, which are specified by environment variables to simplify maintenance of tests:

• playback (default) - always use the cache, throw an error if not found in cache
• cache - try the cache, fallback to the network if not found and add the new response
• record - avoid the cache, always use the network and store the new response

Simply set the VCR_MODE environment variable to whatever mode you want when running the tests.

I evaluated scotch before and wanted to take it further but ended up starting clean for a couple of reasons:

• the use of F# - I wasn't in the mood to re-learn F#, I just wanted to get this idea out there
• putting the replay/recording state in the API isn't something I'm a fan of - I wanted to instead use environment variables so the tests remained simpler.

While it's early days (and I'm not sure if this will even reach production usage) there's already a lot of prior art in here which I've used for research as part of starting this:

• The contributors to the vcr gem
• @philschatz for his work on fetch-vcr
• @mleech for his work on scotch

• probably a bunch of other things