diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index cb1cf5b..70a6cab 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -36,10 +36,10 @@ jobs:
         python-version: ${{ matrix.python-version }}
 
     - name: Install deps
-      run: python -mpip install -r requirements.txt
+      run: python -mpip install -r requirements-dev.txt
 
     - name: Test
-      run: python -munittest
+      run: python -mcoverage run --branch -m unittest && python -mcoverage report --fail-under=100
 
   pre-commit:
     runs-on: ubuntu-20.04
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..1515a5e
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,11 @@
+.PHONY: coverage
+coverage:
+	python3 -mcoverage run --branch -m unittest
+	python3 -mcoverage html
+	python3 -mcoverage annotate
+	python3 -mcoverage report --fail-under=100
+
+# Copyright (C) 2021 Jeff Epler <jepler@gmail.com>
+# SPDX-FileCopyrightText: 2021 Jeff Epler
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
diff --git a/requirements-dev.txt b/requirements-dev.txt
index cf596f7..738fbfd 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -3,5 +3,6 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 adafruit-circuitpython-datetime
 beautifulsoup4
+coverage
 pre-commit
 requests