Before: runtime ale_linters/python/pylint.vim call ale#test#SetDirectory('/testplugin/test/command_callback') let b:command_tail = ' --output-format text --msg-template="{path}:{line}:{column}: {msg_id} ({symbol}) {msg}" --reports n %s' After: call ale#test#RestoreDirectory() call ale#linter#Reset() let g:ale_python_pylint_executable = 'pylint' let g:ale_python_pylint_options = '' let g:ale_python_pylint_use_global = 0 Execute(The pylint callbacks should return the correct default values): AssertEqual \ 'pylint', \ ale_linters#python#pylint#GetExecutable(bufnr('')) AssertEqual \ '''pylint'' ' . b:command_tail, \ ale_linters#python#pylint#GetCommand(bufnr('')) Execute(The pylint executable should be configurable, and escaped properly): let g:ale_python_pylint_executable = 'executable with spaces' AssertEqual \ 'executable with spaces', \ ale_linters#python#pylint#GetExecutable(bufnr('')) AssertEqual \ '''executable with spaces'' ' . b:command_tail, \ ale_linters#python#pylint#GetCommand(bufnr('')) Execute(The pylint command callback should let you set options): let g:ale_python_pylint_options = '--some-option' AssertEqual \ '''pylint'' --some-option' . b:command_tail, \ ale_linters#python#pylint#GetCommand(bufnr('')) Execute(The pylint callbacks shouldn't detect virtualenv directories where they don't exist): silent execute 'file ' . fnameescape(g:dir . '/python_paths/no_virtualenv/subdir/foo/bar.py') AssertEqual \ 'pylint', \ ale_linters#python#pylint#GetExecutable(bufnr('')) AssertEqual \ '''pylint'' ' . b:command_tail, \ ale_linters#python#pylint#GetCommand(bufnr('')) Execute(The pylint callbacks should detect virtualenv directories): silent execute 'file ' . fnameescape(g:dir . '/python_paths/with_virtualenv/subdir/foo/bar.py') AssertEqual \ g:dir . '/python_paths/with_virtualenv/env/bin/pylint', \ ale_linters#python#pylint#GetExecutable(bufnr('')) AssertEqual \ ''''. g:dir . '/python_paths/with_virtualenv/env/bin/pylint'' ' . b:command_tail, \ ale_linters#python#pylint#GetCommand(bufnr('')) Execute(You should able able to use the global pylint instead): silent execute 'file ' . fnameescape(g:dir . '/python_paths/with_virtualenv/subdir/foo/bar.py') let g:ale_python_pylint_use_global = 1 AssertEqual \ 'pylint', \ ale_linters#python#pylint#GetExecutable(bufnr('')) AssertEqual \ '''pylint'' ' . b:command_tail, \ ale_linters#python#pylint#GetCommand(bufnr(''))