[platform-releng-dev] again on session tests

[Rafael Chaves <Rafael_Chaves@xxxxxxxxxx>]

Platform/Core has been doing some work on running JUnit tests that end up
spawning a second instance of Eclipse, or "session tests". There is a lot
of scenarios that can only be tested with session tests, as startup
performance tests.

We have been doing some work in that area, and were curious if others had
the same need, and what approach was (or is planned to be) used to support
that.

Here is the approach we are taking:
- session tests use a special SessionTestSuite class to build their test
suites
- session tests are actually just proxies for the actual tests that know
which plug-in/class/method implements the test case
- when a session test is run, it launches a second instance of Eclipse to
run a application that is/has a test runner. This test runner will run that
single test case and report back the test result to the original instance
using a socket (right now we use org.eclipse.pde.junit.runtime test
applications and protocol for doing that, but it causes an undesirable
dependency on a non-platform plug-in). Once the test case has finished,
this second Eclipse instance terminates
- back to the original instance, we check whether the test failed/passed.
If it failed, we fake a corresponding error/failure to occur at the proxy
test, so it is reported as a regular test error/failure to the JUnit
framework

This way, session tests don't need any special support other than using the
SessionTestSuite class when building their test suites. Also, the current
support for running automated tests as part of the RelEng test framework or
by using the PDE/JDT support in the SDK still works.

Any feedback is welcome.

Rafael