feat: Stage 5 of nox implementation - adding coverage targets (#479)

.coveragerc

@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright 2020 Google LLC
+#
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+[run]
+branch = True
+
+[report]
+fail_under = 100
+show_missing = True
+exclude_lines =
+    # Re-enable the standard pragma
+    pragma: NO COVER
+    # Ignore debug-only repr
+    def __repr__
+    # Ignore abstract methods
+    raise NotImplementedError
+omit =
+  */site-packages/*.py

noxfile.py

@@ -69,6 +69,13 @@ def default(session):
     session.run(
         "py.test",
         "--quiet",
+        "--cov=django_spanner",
+        "--cov=spanner_dbapi",
+        "--cov=tests.spanner_dbapi",
+        "--cov-append",
+        "--cov-config=.coveragerc",
+        "--cov-report=",
+        "--cov-fail-under=0",
         os.path.join("tests", "spanner_dbapi"),
         *session.posargs
     )
@@ -80,6 +87,18 @@ def unit(session):
     default(session)
 
 
+@nox.session(python="3.8")
+def cover(session):
+    """Run the final coverage report.
+
+    This outputs the coverage report aggregating coverage from the unit
+    test runs (not system test runs), and then erases coverage data.
+    """
+    session.install("coverage", "pytest-cov")
+    session.run("coverage", "report", "--show-missing", "--fail-under=20")
+    session.run("coverage", "erase")
+
+
 @nox.session(python="3.8")
 def docs(session):
     """Build the docs for this library."""