Why Wiremock?

You've a requirement where your application needs to be integrated with External APIs, and

• When External APIs are not always available
• When External APIs incur cost on every hit
• And to simulate faults including all 5XX errors, you require downtime for External APIs
• When your application needs Integration Tests with External APIs

Then, Wiremock comes into action to act as Mock Server which can serve all the External APIs without downtime, and in a cost effective manner.

Scope

We'll explore simple way to mocking webservices/ APIs with WireMock. The whole setup in this exercise is purely file (JSON) based, won't uses any code. Focus will be more on how to use mappings and __files. To know more about running Wiremock as standalone process may refer to http://wiremock.org/docs/running-standalone/

Here I'll walk you through with help of Docker Technologies, as the demand for Containerization is High. Follow readme, once you checkout branch for each section.

Exercise APIs

Import Postman Collection for quick links https://www.getpostman.com/collections/acffac443a2bb5110a33

Boilerplate

This section focuses on minimalistic setup of Wiremock. Developers who are exploring for the first time go with this.

git checkout https://github.com/whyaneel/wiremock.git

cd wiremock

git checkout boilerplate

• You'll have Wiremock UP & RUNNING
• You'll run GET mock
• You'll run POST mock (Simulate 200, 400, 500)
• You'll see the need for dynamic responses, first go though http://wiremock.org/docs/response-templating/ and then follow Response Templating section below for examples.

Response Templating

This section gives you examples with the power of Response Templating. Developers who want to tweak to get most out of Wiremock go with this. Observe mappings and __files from rt folder.

git checkout https://github.com/whyaneel/wiremock.git

cd wiremock

git checkout response-templating

• You'll run GET mock with dynamic response with now
• You'll run GET mock with dynamic response from a file with bodyFileName
• You'll run POST mock with dynamic response with jsonPath against a request.body
• You'll run POST mock with dynamic response from a file with bodyFileName
• You'll run POST mock with fault simulation with fixedDelayMilliseconds, for more go though http://wiremock.org/docs/simulating-faults/

Bonus

Let's say your application uses Docker for your N microservices [ms] architecture and only 1 or few ms (consumer-service) need to connect with External APIs (i.e. Wiremock server, mock-runner) and rest of ms should be isolated, then take the advantage of Bridge Network.

git checkout https://github.com/whyaneel/wiremock.git

cd wiremock

git checkout docker2docker

• You'll run GET mock with response templating feature proxyBaseUrl, this is just to simulate a call to mock-runner, Ideally you can use RestTemplate (http) for Java application, or Curl for shell application from your consumer-service
• You'll see consumer-service communicating with mock-runner using internal port via mockrunner_bridge network

You've questions?

Check out Google Group https://groups.google.com/g/wiremock-user/, most of the use cases are present, otherwise I'm happy to help.

👏 Hope you learnt some basics of Wiremock