The creators of http4k takes testing very seriously - so seriously that there really isn't that much to say here! The API has been designed to make it as simple as possible to test both individual endpoints and entire applications in a consistent fashion, which is aided by remembering that:

  1. The input and output Request/Response objects are immutable.
  2. HttpHandlers are just functions.
  3. An entire http4k application is just an HttpHandler.

Because of the above, there really isn't much required in the way of "testing infrastructure" - no magic containers or test fixtures that you might find in other frameworks. Testing is just matter of calling the correct function! Additionally, because the server and client HttpHandler interfaces are symmetrical - moving between in and out of container contexts (or indeed even to another HTTP framework entirely) is just a matter of switching out the HttpHandler implementation from the constructed app (out of container) to an HTTP client (in-container).

That said, possibly the most useful thing is to demonstrate the process that we have developed to test micro-services. A simple example of the development process can be found here.

Testing modules

We have developed the following modules to help with testing:

  • http4k-testing-hamkrest: a set of composable Hamkrest matchers for matching http4k message objects against.
  • http4k-testing-kotest: a set of composable Kotest matchers for matching http4k message objects against.
  • http4k-testing-webdriver: an ultra-lightweight Selenium WebDriver implementation which can be used to test-drive http4k apps (ie. HttpHandlers).
  • http4k-testing-approval: JUnit 5 extensions for Approval testing of http4k Request and Response messages.
  • http4k-testing-chaos: API for declaring and injecting failure modes into http4k applications, allowing modelling and hence answering of "what if" style questions to help understand how code fares under failure conditions such as latency and dying processes.
  • http4k-testing-servitium: a fully featured implementation of the Servirtium solution for Service Virtualization testing approach.