Before: call ale#assert#SetUpLinterTest('eruby', 'erubi') After: call ale#assert#TearDownLinterTest() Execute(Executable should not contain any filter code by default): call ale#test#SetFilename('../ruby_fixtures/not_a_rails_app/file.rb') AssertLinter 'ruby', [ \ 'ruby -r erubi/capture_end -e ' . ale#Escape('""'), \ 'ruby -r erubi/capture_end -e ' . ale#Escape('puts Erubi::CaptureEndEngine.new($stdin.read).src') . '< %t | ruby -c', \] Execute(Executable should filter invalid eRuby when inside a Rails project): call ale#test#SetFilename('../ruby_fixtures/valid_rails_app/app/views/my_great_view.html.erb') AssertLinter 'ruby', [ \ 'ruby -r erubi/capture_end -e ' . ale#Escape('""'), \ 'ruby -r erubi/capture_end -e ' . ale#Escape('puts Erubi::CaptureEndEngine.new($stdin.read.gsub(%{<%=},%{<%}), nil, %{-}).src') . '< %t | ruby -c', \] Execute(Command should be blank if the first command in the chain returns output): GivenCommandOutput [ \ "/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- erubi/capture_end (LoadError)", \ " from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'", \] AssertLinter 'ruby', [ \ 'ruby -r erubi/capture_end -e ' . ale#Escape('""'), \ '', \]