diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..322c005
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,2 @@
+tests:
+	pytest
diff --git a/test_pytheory.py b/test_pytheory.py
index a80c915..0c82db7 100644
--- a/test_pytheory.py
+++ b/test_pytheory.py
@@ -21,3 +21,12 @@ def test_tone_addition():
         Tone.from_string("C4", system=pytheory.SYSTEMS["western"]).add(12).full_name
         == "C5"
     )
+
+
+def test_tone_subtraction():
+    assert (
+        Tone.from_string("C5", system=pytheory.SYSTEMS["western"])
+        .subtract(12)
+        .full_name
+        == "C4"
+    )