Tests if we are context safe : can we switch objects in the context
and re-merge the template safely.
NOTE:
This class should not extend RuntimeTestCase because this test
is run from the VelocityTestSuite which in effect a runtime
test suite and the test suite initializes the Runtime.
Easily add test cases which evaluate templates and check their output.
NOTE:
This class DOES NOT extend RuntimeTestCase because the TemplateTestSuite
already initializes the Velocity runtime and adds the template
test cases.