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Wiremock and Response Transformer

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Wiremock and Response Transformer

This article will help you learn about Wiremock's Response Transformer and how to hook it into your tests and use it to modify responses.

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I wanted to test a scenario where:

  • For the first x calls, respond with y
  • Then, for x+1, respond with z

Wiremock by itself doesn't provide a direct way to stub different responses akin to Mockito's thenReturn or Spock's multiple stubs. Wiremock, however, provides a ResponseTransformer. I used Wiremock's ResponseTransformer to store state, and return y by default but return z on x+1 try.

  static class SuccessfulAtLastTransformer extends ` {

        int count = 1

        SuccessfulAtLastTransformer() {}

        @Override
        ResponseDefinition transform(
                final Request request, final ResponseDefinition responseDefinition, final FileSource fileSource) {

            if (request.getUrl().contains("/customer/cust1234")) {
                if (count == 3) {
                    def responseJson = new JsonSlurper().parseText(responseDefinition.body)
                    // Set the customerId on the final try
                    responseJson.customerCar = "toyota"
                    def newRequestBody = JsonOutput.toJson(responseJson)
                    return new ResponseDefinitionBuilder()
                            .withStatus(200)
                            .withBody(newRequestBody)
                            .build()
                }

                return new ResponseDefinitionBuilder()
                        .withHeader("COUNT", count++ as String)
                        .withStatus(200)
                        .withBody(responseDefinition.body)
                        .build()
            }

            return responseDefinition
        }

        @Override
        boolean applyGlobally() {
            return false
        }

        @Override
        String name() {
            return "SuccessfulAtLastTransformer"
        }
    }

Line #1: extend import com.github.tomakehurst.wiremock.extension.ResponseTransformer

Line #8: Override the transform function.

Line #11: Check if this is the API you are interested in.

Line #12: Check if the count has reached a certain threshold, and if so, then add customerCar property to response JSON.

Line #23: Add count to the response header. That acts as our state storage. Once the count will reach x in this case 3, then change the response (line #13).

Line #34: Set apply globally false, i.e. don't use this ResponseTransformer as an interceptor anywhere else but where I put it.

Line #40: Give your transformer a name.

Once you have defined a ResponseTransformer like above, you can then attach it to the Wiremock instance, like so:

@Shared  
def customerServiceMock =  
      wireMockConfig()
     .port(8090)
     .extensions(SuccessfulAtLastTransformer)

Done.

Please let me know if you have any questions or if there's a better way to do the same thing in Wiremock via comments on this post.

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Topics:
wiremock ,devops ,testing

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