It's possible that you need several modules to manage the dependencies properly.
tapestry-test contains EasyMock/TestNG code and general test code such as TapestryTestConstants
tapestry-selenium includes the selenium code (and depends on tapestry-test)
If you want to be really serious about dependencies and what you force clients to include (which is more important in the OSGi world), you could break the modules down further:
tapestry-test - generic test-related code for Tapestry
tapestry-easymock - adds easymock specific extensions for working with Tapestry
tapestry-testng - enhancements to TestNG to simplify testing Tapestry
tapestry-selenium - enhancements to Selenium to simplify testing in Tapestry
I'm not saying that module breakdown is correct, but I'm suggesting that having more modules at finer granularity is something to consider - remember some people prefer Mockito to EasyMock; some people prefer JUnit4 to TestNG; and finer-grain modules give more flexibility and choice.