Before: Save g:ale_go_gofmt_executable Save g:ale_go_gofmt_options " Use an invalid global executable, so we don't match it. let g:ale_go_gofmt_executable = 'xxxinvalid' let g:ale_go_gofmt_options = '' call ale#test#SetDirectory('/testplugin/test/fixers') After: Restore call ale#test#RestoreDirectory() Execute(The gofmt callback should return the correct default values): call ale#test#SetFilename('../go_files/testfile.go') AssertEqual \ { \ 'read_temporary_file': 1, \ 'command': ale#Escape('xxxinvalid') \ . ' -l -w' \ . ' %t', \ }, \ ale#fixers#gofmt#Fix(bufnr('')) Execute(The gofmt callback should include custom gofmt options): let g:ale_go_gofmt_options = "-r '(a) -> a'" call ale#test#SetFilename('../go_files/testfile.go') AssertEqual \ { \ 'read_temporary_file': 1, \ 'command': ale#Escape('xxxinvalid') \ . ' -l -w' \ . ' ' . g:ale_go_gofmt_options \ . ' %t', \ }, \ ale#fixers#gofmt#Fix(bufnr(''))