Sunday, 24 July 2016

Testing Apache Camel routes

Running Apache Camel on top of Spring is quite popular nowadays and there is a multitude of resources on how to create the routes. However, sooner or later you will want to test the routes and this is where people usually hit a brick wall, because the documentation is a bit confusing. If you're still trying to find a good way to test your routes, then read on.

A simple route

We are using 3 queues: seda:groceries, seda:fruits and seda:vegetables. In case you're wondering what SEDA is, it's just an in-memory queue provided by Camel and it can be replaced by anything else like JMS or RabbitMQ, the principle stays the same.
The type of objects pushed into the groceries queue is checked via Camel's choice() construct and the fruits are redirected into the fruits queue, while the vegetables are redirected into the vegetables queue. The fruits queue is processed by FruitProcessor and the vegetable queue is processed by VegetableProcessor.

The test setup

In order to test the routes, we need to start Camel, which is not possible using the production configuration, considering the fact that Camel will connect to various third party services. Also, we need to make sure that we don't run the real processors, because we only want to test the routes.

This is the test setup, which is actually the complicated part of all this:

A few essential points for the test setup:
  1. We are using CamelSpringJUnit4ClassRunner to run the tests
  2. The test has its own configuration, defined in the ContextConfig inner class, which extends SingleRouteCamelConfiguration
  3. The route() method in ContextConfig() defines the route builder class that we are testing
  4. All the processors are defined as beans and they are mocked by using Camel's MockEndpoint. That allows us to replace the actual processors with mocks and make assertions on how the messages are travelling through the routes.
  5. The mock processors are autowired into the test class so that assertions can be made against them

The tests

After the setup is complete, the actual tests are quite straightforward:
  1. When I push a Fruit object into the groceries queue, I would like the FruitProcessor to process the message
  2. When I push a Vegetable object into the groceries queue, I would like the VegetableProcessor to process the message
This is the actual code:
There are many ways to go about testing the routes, but the setup and test strategy remain the same. I hope you found this useful, if you did then please share. The maven project is available here.

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