Add tests for invert function

Add unit tests for the invert function to verify its behavior with various inputs.

Author: mrafeie

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,18 @@
+const invert = require("./invert.js");
+
+test("should swap keys and values in an object", () => {
+  expect(invert({ a: 1, b: 2 })).toEqual({
+    1: "a",
+    2: "b",
+  });
+});
+
+test("should invert an object with a single key-value pair", () => {
+  expect(invert({ x: 10 })).toEqual({
+    10: "x",
+  });
+});
+
+test("should return an empty object when passed an empty object", () => {
+  expect(invert({})).toEqual({});
+});