add bare dependencies test

Author: basnijholt

tox.ini

@@ -1,7 +1,7 @@
 
 [tox]
 isolated_build = True
-envlist = clean,py{36,37,38},report,pre-commit
+envlist = clean,py{36,37,38},bare{36,37,38},report,pre-commit
 
 [pytest]
 testpaths = adaptive
@@ -36,6 +36,13 @@ depends =
   {py36,py37,py38}: clean
   report: {py36,py37,py38}
 
+[testenv:bare]
+deps = .[testing]
+commands =
+  pytest
+depends =
+  {bare36,bare37,bare38}: clean
+
 [testenv:report]
 deps = coverage
 skip_install = true