C# - How to set up scenarios with Wiremock - with examples

Sometimes we want more than just a simple stub from wiremock, sometimes we want to create a scenario. We want Wiremock to do something different when we call it a second or third time. A common scenario is a request that first fails, but on second try is OK. A use case for this is that every connection will transiently fail at some point and Wiremock can be used to test this scenario.

Below I have created a scenario that first returns a HTTP 500 status code, then a 404 status code and at the end a 200 status code.

//Setup first request to return 500
server
    .Given(
        Request.Create()
            .WithPath("/weatherforecastbackend")
            .UsingGet()
    )
    .InScenario("my-scenario")
    .WillSetStateTo("my-scenario-step2")
    .RespondWith(
        Response.Create()
            .WithStatusCode(500)
            .WithBody("wiremock: this is a 500!")
    );

//Setup second request to return 404
server
    .Given(
        Request.Create()
            .WithPath("/weatherforecastbackend")
            .UsingGet()
    )
    .InScenario("my-scenario")
    .WhenStateIs("my-scenario-step2")
    .WillSetStateTo("my-scenario-step3")
    .RespondWith(
        Response.Create()
            .WithStatusCode(404)
            .WithBody("wiremock: this is a 404!")
    );

//Setup third request to return 200
server
    .Given(
        Request.Create()
            .WithPath("/weatherforecastbackend")
            .UsingGet()
    )
    .InScenario("my-scenario")
    .WhenStateIs("my-scenario-step3")
    .RespondWith(
        Response.Create()
            .WithStatusCode(200)
            .WithBody("This is a body")
    );

Note that in the above I always return a body, this is to tell myself that this is wiremock responding, so I do not get the 404 mixed up with a regular 404 when debugging :)

For scenarios in Wiremock you need to set each request matcher to belong to a given scenario, for example: .InScenario("my-scenario"). You can then set which State in the scenario this request matcher belongs to, for example: .WhenStateIs("my-scenario-step2"). Lastly, you can set which state you wish to transition to once the current state is triggered, for example: .WillSetStateTo("my-scenario-step3").

We can test the above with a simple unit test:

var httpClient = new HttpClient();
var firstRequest = await httpClient.GetAsync(
   "http://localhost:58116/weatherforecastbackend");
Assert.Equal(HttpStatusCode.InternalServerError, firstRequest.StatusCode);

var secondRequest = await httpClient.GetAsync(
   "http://localhost:58116/weatherforecastbackend");
Assert.Equal(HttpStatusCode.NotFound, secondRequest.StatusCode);

var thirdRequest = await httpClient.GetAsync(
   "http://localhost:58116/weatherforecastbackend");
Assert.Equal(HttpStatusCode.OK, thirdRequest.StatusCode);
Assert.Equal("This is a body", await thirdRequest.Content.ReadAsStringAsync());

The result of this can be seen in the below image:

That is basically all there is to it, I hope you enjoyed this post, let me know in the comments what you think! :)