test: added supertest

src/utils/addition.test.ts

@@ -0,0 +1,9 @@
+import { addition } from './addition';
+
+describe('call', () => {
+  it('returns the input value increased by one', async () => {
+    const response = addition(3);
+
+    expect(response).toBe(4);
+  });
+});

src/utils/addition.ts

@@ -0,0 +1,8 @@
+/**
+ * Format a response message containing a user input.
+ * @param number - The user input value.
+ * @returns The value increased by one.
+ */
+export function addition(value: number) {
+  return value + 1;
+}