Before: Save g:ale_html_rustywind_executable Save g:ale_html_rustywind_options " Use an invalid global executable, so we don't match it. let g:ale_html_rustywind_executable = 'xxxinvalid' let g:ale_html_rustywind_options = '' call ale#test#SetDirectory('/testplugin/test/fixers') After: Restore call ale#test#RestoreDirectory() Execute(The rustywind callback should return the correct default values): call ale#test#SetFilename('../test-files/rustywind/test.html') AssertEqual \ { \ 'command': ale#Escape('xxxinvalid') \ . ' --stdin', \ }, \ ale#fixers#rustywind#Fix(bufnr('')) Execute(The rustywind callback should include custom rustywind options): let g:ale_html_rustywind_options = "--custom-regex some-regex" call ale#test#SetFilename('../test-files/rustywind/test.html') AssertEqual \ { \ 'command': ale#Escape('xxxinvalid') \ . ' ' . g:ale_html_rustywind_options \ . ' --stdin', \ }, \ ale#fixers#rustywind#Fix(bufnr(''))