using (var stub = new ApiStub())
{
    stub.Get(
        "/testget",
        (req, args) => "testresponse");

    stub.Start();

    var result = await httpClient.GetAsync(new UriBuilder(new Uri(stub.Address)) { Path = "/testget" }.Uri);

    // resultString will contain "testresponse"
    var resultString = await result.Content.ReadAsStringAsync();
}

using (var stub = new ApiStub())
{
    stub.Get(
        "/testget/{arg1}",
        (req, args) => $"testresponse arg1: {args.Route.arg1} queryArg1: {args.Query.queryArg1}");

    stub.Start();

    var result = await httpClient.GetAsync(
        new UriBuilder(new Uri(stub.Address)) { Path = "/testget/orange", Query = "?queryArg1=melon" }.Uri);

    // resultString will contain "testresponse arg1: orange queryArg1: melon"
    var resultString = await result.Content.ReadAsStringAsync();
}

using (var stub = new ApiStub())
{
    stub.Post(
        "/testpost",
        (req, args) => $"testresponse body: {args.Body.ReadAsString()}");

    stub.Start();

    var result = await httpClient.PostAsync(
        new UriBuilder(new Uri(stub.Address)) { Path = "/testpost" }.Uri,
        new StringContent("orange"));

    // resultString will contain "testresponse body: orange"
    var resultString = await result.Content.ReadAsStringAsync();
}

using (var stub = new ApiStub())
{
    stub.Request(HttpMethod.Options)
        .IfRoute("/testoptions")
        .Response((req, args) => "testresponse");

    stub.Start();

    var result = await httpClient.SendAsync(
        new HttpRequestMessage
        {
            RequestUri = new UriBuilder(new Uri(stub.Address)) { Path = "/testoptions" }.Uri,
            Method = HttpMethod.Options
        });

    // resultString will contain "testresponse"
    var resultString = await result.Content.ReadAsStringAsync();
}