Before: Save g:ale_python_reorder_python_imports_executable Save g:ale_python_reorder_python_imports_options " Use an invalid global executable, so we don't match it. let g:ale_python_reorder_python_imports_executable = 'xxxinvalid' let g:ale_python_reorder_python_imports_options = '' call ale#test#SetDirectory('/testplugin/test/fixers') let b:bin_dir = has('win32') ? 'Scripts' : 'bin' After: Restore unlet! b:bin_dir call ale#test#RestoreDirectory() Execute(The reorder_python_imports callback should return the correct default values): AssertEqual \ 0, \ ale#fixers#reorder_python_imports#Fix(bufnr('')) silent execute 'file ' . fnameescape(g:dir . '/../test-files/python/with_virtualenv/subdir/foo/bar.py') AssertEqual \ { \ 'command': ale#Escape(ale#path#Simplify(g:dir . '/../test-files/python/with_virtualenv/env/' \ . b:bin_dir . '/reorder-python-imports')) . ' -', \ }, \ ale#fixers#reorder_python_imports#Fix(bufnr('')) Execute(The reorder_python_imports callback should respect custom options): let g:ale_python_reorder_python_imports_options = '--py3-plus' AssertEqual \ 0, \ ale#fixers#reorder_python_imports#Fix(bufnr('')) silent execute 'file ' . fnameescape(g:dir . '/../test-files/python/with_virtualenv/subdir/foo/bar.py') AssertEqual \ { \ 'command': ale#Escape(ale#path#Simplify(g:dir . '/../test-files/python/with_virtualenv/env/' \ . b:bin_dir . '/reorder-python-imports')) . ' --py3-plus -', \ }, \ ale#fixers#reorder_python_imports#Fix(bufnr(''))