Invokation:
$ casperjs --includes=included_script.js test main_test_script.js
Output:
Test file: main_test_script.js
plop
PASS Page title is "Google"
PASS 1 tests executed, 1 passed, 0 failed.
Could you please try to switch to latest master? lots of fixes happened recently, while I don't see any reason for your issue being covered, it's maybe worth the effort…