Before: call ale#assert#SetUpLinterTest('python', 'pyflakes') let b:bin_dir = has('win32') ? 'Scripts' : 'bin' After: unlet! b:bin_dir unlet! b:executable call ale#assert#TearDownLinterTest() Execute(The pyflakes command callback should return default string): AssertLinter 'pyflakes', ale#Escape('pyflakes') . ' %t' Execute(The pyflakes executable should be configurable): let g:ale_python_pyflakes_executable = '~/.local/bin/pyflakes' AssertLinter '~/.local/bin/pyflakes', \ ale#Escape('~/.local/bin/pyflakes') . ' %t' Execute(The pyflakes 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 . '/pyflakes' \) AssertLinter b:executable, ale#Escape(b:executable) . ' %t' Execute(You should be able to override the pyflakes virtualenv lookup): call ale#test#SetFilename('python_paths/with_virtualenv/subdir/foo/bar.py') let g:ale_python_pyflakes_use_global = 1 AssertLinter 'pyflakes', ale#Escape('pyflakes') . ' %t' Execute(Setting executable to 'pipenv' appends 'run pyflakes'): let g:ale_python_pyflakes_executable = 'path/to/pipenv' AssertLinter 'path/to/pipenv', \ ale#Escape('path/to/pipenv') . ' run pyflakes %t',