Imported from dennisdoomen/mockly (SKILL.md). Install upstream with npx skills add dennisdoomen/mockly. Copyright stays with the author.

Mockly

Fluent HTTP mocking library for .NET. Intercepts HttpClient calls via a custom HttpMessageHandler. Unmatched requests throw UnexpectedRequestException by default (FailOnUnexpectedCalls = true). Default base address: https://localhost/.

Setup

var mock = new HttpMock();
mock.ForGet().WithPath("/api/users").RespondsWithStatus(HttpStatusCode.OK);
HttpClient client = mock.GetClient(); // or mock.GetClientFactory()

HTTP Verbs

// Convenience methods per verb (each also has a "(urlPattern)" overload)
mock.ForGet();
mock.ForPost();
mock.ForPut();
mock.ForPatch();
mock.ForDelete();
mock.ForHead();
mock.ForOptions();

// Generic entry point for any (including non-standard) verb
mock.For(HttpMethod.Get).WithPath("/api/data").RespondsWithStatus(HttpStatusCode.OK);
mock.For(new HttpMethod("PROPFIND"), "https://localhost/dav/*").RespondsWithStatus(HttpStatusCode.OK);

URL Matching

// Exact path (leading slash optional); * is wildcard
mock.ForGet().WithPath("/api/users/*").RespondsWithStatus(HttpStatusCode.OK);

// Query: omitting WithQuery() rejects requests that include a query string
mock.ForGet().WithPath("/api/search").WithQuery("?q=*").RespondsWithStatus(HttpStatusCode.OK);
mock.ForGet().WithPath("/api/search").WithAnyQuery().RespondsWithStatus(HttpStatusCode.OK);
mock.ForGet().WithPath("/api/search").WithoutQuery().RespondsWithStatus(HttpStatusCode.OK);

// Scheme / host
mock.ForGet().ForHttps().ForHost("api.example.com").WithPath("/data").RespondsWithStatus(HttpStatusCode.OK);
mock.ForGet().ForHttp().ForAnyHost().WithPath("/data").RespondsWithStatus(HttpStatusCode.OK);

// Full-URL shorthand (scheme + host + path + query, all support *)
mock.ForGet("https://api.example.com/users/*?q=*").RespondsWithStatus(HttpStatusCode.OK);
mock.ForPatch("http://*.example.com/*").RespondsWithStatus(HttpStatusCode.OK);

Request Body Matching

mock.ForPost().WithPath("/api/data").WithBody("*keyword*").RespondsWithStatus(HttpStatusCode.NoContent);
mock.ForPost().WithPath("/api/data").WithBody(new { name = "John" }).RespondsWithStatus(HttpStatusCode.NoContent); // JSON object
mock.ForPost().WithPath("/api/data").WithBodyMatchingJson("{\"name\":\"John\"}").RespondsWithStatus(HttpStatusCode.NoContent);
mock.ForPost().WithPath("/api/data").WithBodyMatchingRegex(".*keyword.*").RespondsWithStatus(HttpStatusCode.NoContent);

// Custom predicate (sync or async) — use .With() for custom body or URI checks
mock.ForPost().WithPath("/api/data").With(req => req.Body!.Contains("keyword")).RespondsWithStatus(HttpStatusCode.NoContent);

// Body matching (WithBody, WithBodyMatchingJson, etc.) only works when the Content-Type is recognized as
// textual (text/*, multipart/*, application/json, application/xml, and similar). For an unrecognized or
// binary-looking Content-Type that is actually text, opt in with TreatBodyAsTextual():
mock.ForPost().WithPath("/api/data").WithBody("*keyword*").TreatBodyAsTextual().RespondsWithStatus(HttpStatusCode.NoContent);

Header Matching

mock.ForGet().WithPath("/api/secure").WithHeader("X-API-Key").RespondsWithStatus(HttpStatusCode.OK);
mock.ForGet().WithPath("/api/secure").WithHeader("X-Trace-Id", "abc-*").RespondsWithStatus(HttpStatusCode.OK);
mock.ForGet().WithPath("/api/auth").WithBearerToken().RespondsWithStatus(HttpStatusCode.OK);
mock.ForPost().WithPath("/api/json").WithContentType("application/json").RespondsWithStatus(HttpStatusCode.OK);

Responses

mock.ForDelete().WithPath("/api/items/1").RespondsWithStatus(HttpStatusCode.NoContent);
mock.ForGet().WithPath("/api/user").RespondsWithJsonContent(new { Id = 1, Name = "Alice" });
mock.ForGet().WithPath("/api/user").RespondsWithJsonContent(HttpStatusCode.Created, new { Id = 1 });
mock.ForGet().WithPath("/api/text").RespondsWithContent("Hello"); // 200 OK, application/json
mock.ForGet().WithPath("/api/text").RespondsWithContent(HttpStatusCode.OK, "<xml/>", "text/xml");
mock.ForGet().WithPath("/api/empty").RespondsWithEmptyContent(); // 204 No Content
mock.ForGet().WithPath("/api/binary").RespondsWith(new ByteArrayContent(bytes));
mock.ForGet().WithPath("/api/custom").RespondsWith(_ => new HttpResponseMessage(HttpStatusCode.OK));

// OData v4: wraps in { "value": [...] }
mock.ForGet().WithPath("/odata/items").RespondsWithODataResult(new { Id = 1 });
mock.ForGet().WithPath("/odata/items").RespondsWithODataResult(HttpStatusCode.OK, items, "https://localhost/$metadata#Items");

HttpContent instances are reused across calls — use the lambda overload for mocks called multiple times.

Request Capture

// Global log
mock.Requests.HasUnexpectedRequests // bool
mock.Requests.First().WasExpected   // bool; .Uri, .Method, .Body, .Timestamp, .Response also available

// Scoped collection
var captured = new RequestCollection();
mock.ForPatch().WithPath("/api/items/1").CollectingRequestsIn(captured).RespondsWithStatus(HttpStatusCode.NoContent);
captured.Count.Should().Be(1);

Invocation Limits

mock.ForGet().WithPath("/api/once").RespondsWithStatus(HttpStatusCode.OK).Once();
mock.ForGet().WithPath("/api/twice").RespondsWithStatus(HttpStatusCode.OK).Twice();
mock.ForGet().WithPath("/api/data").RespondsWithStatus(HttpStatusCode.OK).Times(3);

mock.AllMocksInvoked.Should().BeTrue();   // true when all mocks hit required count
mock.GetUninvokedMocks();                  // IEnumerable<RequestMock>

Response Latency

// Delay the response to test timeout / cancellation / resilience behavior.
mock.ForGet().WithPath("/slow").RespondsWithStatus(HttpStatusCode.OK).After(TimeSpan.FromSeconds(2));
// A shorter HttpClient.Timeout or a cancelled token throws TaskCanceledException/OperationCanceledException.

Reset / Clear

mock.Reset(); // clears scheme/host inheritance from previous builder; start fresh
mock.Clear(); // removes all configured mocks

FluentAssertions.Mockly (FluentAssertions.Mockly.v8 / .v7)

mock.Should().HaveAllRequestsCalled();
mock.Requests.Should().NotContainUnexpectedCalls();
mock.Requests.Should().NotBeEmpty();
mock.Requests.First().Should().BeExpected();
mock.Requests.First().Should().BeUnexpected();