test: skip if varname is not installed

.github/workflows/python-package.yml

@@ -1,7 +1,7 @@
 # This workflow will install Python dependencies, run tests and lint with a variety of Python versions
 # For more information see: https://help.github.com/actions/language-and-framework-guides/using-python-with-github-actions
 
-name: Python package
+name: Test and Lint
 
 on:
   push:
@@ -16,6 +16,7 @@ jobs:
     strategy:
       matrix:
         python-version: ['3.6', '3.7', '3.8', '3.9']
+        extras: [null, 'varname']
 
     steps:
     - uses: actions/checkout@v2
@@ -27,6 +28,10 @@ jobs:
       run: |
         python -m pip install poetry
         poetry install
+    - name: Install extras
+      if: ${{ matrix.extras }}
+      run: |
+        poetry install --extras ${{ matrix.extras }}
     - name: Format with Black
       run: |
         poetry run black --check --diff sentinel.py

test_sentinel.py

@@ -8,6 +8,13 @@
 
 import sentinel
 
+try:
+    import varname  # type: ignore
+except ImportError:
+    HAS_VARNAME = False
+else:
+    HAS_VARNAME = True
+
 # Must be defined at module-level due to limitations in how the pickle module works :/
 Pickleable = sentinel.create("Pickleable")
 
@@ -144,9 +151,10 @@ def test_copy():
     assert copied[Copyable][1] is not arbitrary_data_structure[Copyable][1]
 
 
-def test_varnames():
+@pytest.mark.skipif(not HAS_VARNAME, reason="varname PyPI package not installed")
+def test_varname():
     """
-    Test support with Python varnames,
+    Tests infering the variable name. Requires varname library be installed.
     """
 
     Dark = sentinel.create()