Refactor contains tests for clarity and consistency

Author: Maryanne-K

Sprint-2/implement/contains.test.js

@@ -20,9 +20,7 @@ test("contains returns true for existing property", () => {
   expect(contains({a: 1, b: 2}, 'a')).toBe(true);
 });
 
-test("contains returns false for non-existent property", () => {
-  expect(contains({a: 1, b: 2}, 'c')).toBe(false);
-});
+
 // Given an empty object
 // When passed to contains
 // Then it should return false
@@ -33,7 +31,7 @@ test("contains returns false for empty object", () => {
 // Given an object with properties
 // When passed to contains with an existing property name
 // Then it should return true
-test("contains returns true for existing property", () => {
+test("returns true when property exists in object", () => {
   expect(contains({a: 1, b: 2}, 'a')).toBe(true);
 });
 // Given an object with properties
@@ -45,6 +43,18 @@ test("contains returns false for non-existent property", () => {
 // Given invalid parameters like an array
 // When passed to contains
 // Then it should return false or throw an error
-test("contains with invalid parameters returns false or throws error", () => {
-  expect(contains([1, 2, 3], 'a')).toBe(false);
+test("contains with invalid input returns false", () => {
+  expect(contains([], 'a')).toBe(false);
+  expect(contains(123, 'a')).toBe(false);
+  expect(contains("string", 'a')).toBe(false);
 });
+
+test("returns false for null input", () => {
+  expect(contains(null, 'a')).toBe(false);
+});
+
+test("returns false for undefined input", () => {
+  expect(contains(undefined, 'a')).toBe(false);
+});
+
+