Try usedevelop in tox

tox.ini

@@ -11,6 +11,7 @@ setenv =
     PYCIF_DATATEST=/tmp/PYCIF_DATA_TEST/
 extras=test
 skipsdist=True
+usedevelop=True
 commands=
     pytest --basetemp={envtmpdir} --cov=pycif --no-cov-on-fail --html reports/pytest-{envname}.html --self-contained-html {posargs}