diff --git a/minus b/minus
new file mode 100644
index 0000000..21cfb1f
--- /dev/null
+++ b/minus
@@ -0,0 +1,4 @@
+function minus(a, b) {
+  return a - b;
+}
+module.exports = minus;
diff --git a/sum.test.js b/sum.test.js
index fd83c00..2e156aa 100644
--- a/sum.test.js
+++ b/sum.test.js
@@ -1,5 +1,5 @@
 const sum = require("./sum");
 
 test("adds 1 + 2 to equal 3", () => {
-  expect(sum(1, 2)).toBe(3);
+  expect(sum(1, 3)).toBe(4);
 });