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TestableHttpClient

GitHub GitHub Workflow Status Nuget CII Best Practices

Creating unittest for code that uses HttpClient can be difficult to test. It requires a custom HttpMessageHandler or a mocked version. TestableHttpClient provides a testable version of HttpMessageHandler and several helper functions to configure the TestableHttpHandler and several ways to assert which requests were made.

How to install

TestableHttpClient is released as a NuGet packages and can be installed via the NuGet manager in VisualStudio or by running the following command on the command line:

dotnet add package TestableHttpClient

How to use TestableHttpClient

The following code block shows the basic use case for asserting that certain requests are made:

TestableHttpMessageHandler testHandler = new();
HttpClient httpClient = new(testHandler); // or testHandler.CreateClient();

var result = await httpClient.GetAsync("http://httpbin.org/status/200");

testHandler.ShouldHaveMadeRequestsTo("https://httpbin.org/*");

The default response is an empty response message with a 200 OK StatusCode, in order to return real content the response need to be configured:

TestableHttpMessageHandler testHandler = new();
testHandler.RespondWith(Responses.Json(new { Hello: "World" }));
HttpClient httpClient = new(testHandler); // or testHandler.CreateClient();

var result = await httpClient.GetAsync("http://httpbin.org/status/200");

testHandler.ShouldHaveMadeRequestsTo("https://httpbin.org/*");

More examples can be found in the IntegrationTests project

URI Patterns

TestableHttpClient supports URI patterns in several places, mainly in:

  • Response routing, where an URI pattern is used for matching the request URI to a response
  • Assertions, where requests can be asserted against an URI pattern.

URI patterns are based on URI's as specified in RFC 3986, but allow the wildcard character * to specify optional parts of an URI.

An URI contains several components:

  • The scheme of an URI is optional, but when given it should end with ://. When not given *:// is assumed.
  • User Information (username:password@) is ignored and is not checked at all.
  • The host is optional and when not given * is assumed. Both IP addresses and registered names are supported.
  • The port is optional, but when ':' is provided after host, it should have a value.
  • The path is optional, but should start with a /. When / is given, it can be followed by a * to match it with any path.
  • Query parameters are optional, when given it should start with a ?.
  • Fragments are ignored, but should start with a #.

URI patterns differ from URI's in the following ways:

  • Any character is allowed, for example: myhost:myport is a valid URI pattern, but not a valid URI. (and this will never match).
  • No encoding is performed, and patterns are matched against the unescaped values of an URI.
  • Patterns are not normalized, so a path pattern /test/../example will not work.

Some examples:

Uri pattern Matches
* Matches any URL
*://*/*?* Matches any URL
/get Matches any URL that uses the path /get
http*://* Matches any URL that uses the scheme http or https (or any other scheme that starts with http)
localhost:5000 Matches any URL that uses localhost for the host and port 5000, no matter what scheme or path is used.

Controlling the behaviour of pattern matching

TestableHttpClient has several options available that let you control different parts of the library. These options can be found on the TestableHttpMessageHandler.Options and are passed to the HttpRepsonseContext and the IHttpRequestMessagesCheck. The options include:

  • JsonSerializerOptions for controlling the serialization of json content
  • UriPatternMatchingOptions for controlling how the URI pattern matching works.

Supported .NET versions

TestableHttpClient is build as a netstandard2.0 library, so theoretically it can work on every .NET version that support netstandard2.0. The following versions are being actively tested and thus supported:

  • .NET Framework 4.6, 4.7 and 4.8
  • .NET 6.0
  • .NET 8.0
  • .NET 9.0

These versions are supported as long as Microsoft supports them, we do our best to test and support newer versions as soon as possible.

Contributing

Please read CONTRIBUTING.md for details on how you can help us out.

Versioning

We use SemVer for versioning. For the versions available, see the releases on this repository.

Note that currently every library will always be released when a new tag is created, even though it might not have any changes.

Authors

See also the list of contributors who participated in this project.

License

This project is released under the MIT license, see LICENSE.md for more information.

Acknowledgments

This project is largely inspired by the HttpTest functionality from Flurl.
A lot of the ideas came from the thread about unit testing HttpClient code in this dotnet issue.