Fix spec_dir lookup when Dir.pwd is not Rails.root

[kurko]

Context

I was able to get this gem to work with my engine by going
inside the test_app dir and running

bundle exec rails spec:javascript

So far so good. The problem is that I don't want to have to run
cd spec/test_app every time to run my Javascript tests. I want to run them
from the engine's grandparent directory so I can include it in my Rakefile for
the entire test suite. In other words, this is my dir tree:

~/engine/
~/engine/spec/javascripts/
~/engine/spec/test_app/spec/javascripts/support/jasmine.yml

Rails.root is always ~/engine/spec/test_app/, regardless of whether
I'm in `~/engine/ or not.

The problem

Look at this line:

[paths].flatten.map { |path| Dir.glob path }.flatten.collect { |path| Rails.root.join(path) }

Dir.glob path, equivalent to Dir.glob("spec/javascripts") returns
true because Dir.pwd is ~/engine/, therefore
~/engine/spec/javascripts exists.

However, the last collect has Rails.root.join("spec_javascript),
which will map to ~/engine/spec/test_app/spec/javascripts, but
there's nothing there (because my test files were configured to
~/engine/spec/javascript).

To "fix that, I put ../javascripts in my yml's spec_dir, but no Dir.glob
just returns false because, in fact, ~/engine/../javascripts doesn't exist.
So, the code is verifying one path and resolving to some other.

The fix

-      [paths].flatten.map { |path| Dir.glob path }.flatten.collect { |path| Rails.root.join(path) }
+      [paths].flatten.map { |path| Dir.glob(Rails.root.join(path)) }.flatten.collect { |path| Rails.root.join(path) }

This fix just makes it cohesive.

I suspect this is in a way connected with
testdouble#102 (to make it work with
engines).