unity-testrunner-playmode-avoid-compile-error
user must control PlayMode Test code
Unity's ENABLE_PLAYMODE_TESTS_RUNNER
ENABLE_PLAYMODE_TESTS_RUNNER directive means support PlayMode Test Runner.
NOT in PlayMode Test Runner enabled.
Assembly reference nunit
From Unity 5.6 to Unity 2017.3 control by manual.
But after Unity 2017.4, always enabled!
You be able to use Assembly Definition, and control PlayMode Test code, after Unity 2017.3.
all version effect, control by user custom define...