test(set): add set function tests

src/__tests__/set.spec.ts

@@ -0,0 +1,35 @@
+import set from '../set';
+
+describe('set', () => {
+  test('should return a new object not a reference', () => {
+    const obj = {};
+    const result = set(obj, 'a', 1);
+
+    expect(result.a).toBe(1);
+    expect(Object.keys(obj)).toHaveLength(0);
+  });
+
+  test('should set the specified value on the object', () => {
+    const obj = {};
+    const result = set(obj, 'a', 1);
+
+    expect(result.a).toBe(1);
+  });
+
+  test('should use dot notation for the path', () => {
+    const obj = {};
+    const result = set(obj, 'a.b', 1);
+
+    expect(result.a.b).toBe(1);
+  });
+
+  test('should throw TypeError for invalid arguments', () => {
+    const invalidObj: unknown = 'testing';
+    const invalidPath: unknown = 1;
+
+    expect(() => set(invalidObj as OObject, 'test', 'test'))
+      .toThrow(new TypeError('Expected Object, got string testing'));
+    expect(() => set({}, invalidPath as string, 'test'))
+      .toThrow(new TypeError('Expected String, got number 1'));
+  });
+});