casperjs test --includes

included_script.js

casper.echo('plop');

main_test_script.js

casper.start('http://google.com/', function() {
    this.test.assertTitle('Google');
});

casper.run(function() {
    this.test.done();
});

Usage.md

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.    

I'm glad if I helped :)

Now I'm still wondering why it didn't work by your side using 0.6.10 :$