Integration and Functional Testing with Maven 2.0
The Better Builds With Maven book discusses the recommended practice of putting integration tests in a separate module. If at all possible, follow this advice.
Put your Integration tests in a separate module
Better Builds With Maven describes a single example module containing only integration tests. In the case of a multi-module "reactor" project, where each module may need some integration testing, you have some choices available to you.
Create Multiple Integration Test POMs
You can, if you wish, create multiple integration test modules, one for each source module in your project. For example, if you've got two child projects "foo" and "bar", you could create a "foo-integration-test" module and a "bar-integration-test" module to test "foo" and "bar" respectively.
The advantage of doing it this way is that it's very clear which integration tests belong to which project. It's also easy for project owners to know which integration tests they're responsible for. The big drawback here is that you've just doubled the number of POM files in your reactor, which can be difficult to manage. Each project will need to be separately referenced in the root POM.
Put all Integration Tests into One Big Module
This is obviously much simpler to wire up in a POM file; simplicity is a virtue in project management.
The disadvantage of doing it this way is that it tends to separate the integration tests from the code they're attempting to test. As a result, you may find that no one "owns" the integration tests; typically you'll have some one person whose job it is to analyze the integration tests and find bugs. QA is hard, but it's even harder when it's unclear who "owns" test failures.
Alternatives to Isolating the Integration Tests
If for some reason you can't put the integration tests in a separate module, here are some ideas.
Integration Tests Only
If you have only integration tests in the same module as your webapp, you can configure Surefire to skip the test phase, then run in the integration-test phase. See this page.
Both Unit and Integration Tests in the Same Module
If you need to run both unit and integration tests in the same module, it's possible, just not very pretty.
There is only one testSourceDirectory per module, so all of your test classes must reside in one directory structure, usually src/test/java.
In the 'test' phase, configure Surefire to exclude the tests in (for example)
Bind another execution of maven-surefire-plugin to the integration-test phase, and reverse the exclusion pattern.
You can see an example of this in the Shale Usecases example app pom.xml file.
Rumor has it that Maven 2.1 will support something like src/it/java in the integration-test phase, in addition to src/test/java in the test phase.