Before: Save g:ale_toml_tombi_executable Save g:ale_toml_tombi_lint_options " Use an invalid global executable, so we don't match it. let g:ale_toml_tombi_executable = 'xxxinvalid' let g:ale_toml_tombi_lint_options = '' call ale#test#SetDirectory('/testplugin/test/fixers') After: Restore call ale#test#RestoreDirectory() Execute(The tombi lint callback should return the correct default values): AssertEqual \ {'command': ale#Escape('xxxinvalid') . ' lint'}, \ ale#fixers#tombi_lint#Fix(bufnr('')) Execute(The tombi lint callback should include custom options): let g:ale_toml_tombi_lint_options = "--offline" AssertEqual \ {'command': ale#Escape('xxxinvalid') . ' lint --offline'}, \ ale#fixers#tombi_lint#Fix(bufnr(''))