Before: Save g:ale_python_pyls_executable Save g:ale_python_pyls_use_global unlet! g:ale_python_pyls_executable unlet! g:ale_python_pyls_use_global let b:bin_dir = has('win32') ? 'Scripts' : 'bin' call ale#test#SetDirectory('/testplugin/test/command_callback') runtime ale_linters/python/pyls.vim After: Restore unlet! b:bin_dir unlet! b:executable call ale#test#RestoreDirectory() call ale#linter#Reset() Execute(The pyls command callback should return default string): AssertEqual ale#Escape('pyls'), \ ale_linters#python#pyls#GetCommand(bufnr('')) Execute(The pyls executable should be configurable): let g:ale_python_pyls_executable = '~/.local/bin/pyls' AssertEqual ale#Escape('~/.local/bin/pyls'), \ ale_linters#python#pyls#GetCommand(bufnr('')) Execute(The pyls executable should be run from the virtualenv path): call ale#test#SetFilename('python_paths/with_virtualenv/subdir/foo/bar.py') let b:executable = ale#path#Simplify( \ g:dir . '/python_paths/with_virtualenv/env/' . b:bin_dir . '/pyls' \) AssertEqual ale#Escape(b:executable), \ ale_linters#python#pyls#GetCommand(bufnr('')) Execute(You should be able to override the pyls virtualenv lookup): call ale#test#SetFilename('python_paths/with_virtualenv/subdir/foo/bar.py') let g:ale_python_pyls_use_global = 1 AssertEqual ale#Escape('pyls'), \ ale_linters#python#pyls#GetCommand(bufnr(''))