Testing extensions
Testing Camel Quarkus extensions is very similar to testing Camel Quarkus applications. In both cases, the tests interact with a Camel Quarkus application. The main difference is in the purpose of the tested application: when testing extensions, it is there just for the sake of testing. We use it as a means to indirectly verify the functionality of the underlying extension(s).
Anatomy of an extension integration test
The application
The application under test lives under src/main directory of the test module.
It should typically contain one or more Camel routes that utilize the Camel component brought by the extension under test.
If it helps to avoid additional dependencies, using @ConsumerTemplate and/or @ProducerTemplate may be favorable over having a full-fledged route.
Tests
Because native tests run in a process separate from the JVM running the tests, all communication between the tests and the application under test must go over network or some other kind of interprocess communication. We typically use JAX-RS endpoints (on the application side) and RestAssured (on the test side) for this purpose.
As suggested in the Testing user guide, our native tests typically extend their JVM counterparts using the same test code for both JVM and native mode. For this reason we abstain from using CDI and direct call of application code in our tests.
Except for RestAssured, we also use Awaitility for awaiting some state and AssertJ for more advanced assertions.
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As mentioned in Create new extension section,
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Minimal set of dependencies
Keeping the set of test module dependencies as small as possible has two main advantages:
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Less code is faster to compile to native image
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Additional code may introduce some side effects, mainly in native compilation. For instance, an extension A may configure the native compiler in such a way that it causes also extension B to work properly in native mode. However, if B was tested in isolation, it would not work.
Grouping
Some of our test modules have very similar sets of dependencies. While it is important to test them in isolation, running each separately takes quite a lot of time, mainly due to native compilation. In such cases, it may make sense to create a "grouped" module that unifies (using some tooling) several isolated tests. The grouped module may then be preferred in a CI job that validates pull requests, while the isolated tests are run only once a day.
Coverage
When porting a Camel component to Quarkus, we generally do not want to duplicate all the fine grained tests that are often available in Camel already. Our main goal is to make sure that the main use cases work well in native mode. But how can you figure out which are those?
The use cases explained in the given components documentation usually give a good guidance. For example, when writing tests for the SQL extension, you would go to documentation page of the SQL component and try to cover the use cases mentioned there: Treatment of the message body Result of the query, Using StreamList, etc.
In any case, both consumer and producer of the component (if the component supports both) should be covered.
Lightweight functional tests
Especially when testing various configuration setups, having a separate integration test module for each configuration set would be an overkill.
io.quarkus.test.QuarkusUnitTest may suit well for such situations.
A big advantage of this kind of tests is that they are very lightweight and fast. But on the other hand, they are executed only in JVM mode.
Please refer to the Servlet extension for an examples.