test(includes): add includes function tests

src/__tests__/includes.spec.ts

@@ -0,0 +1,42 @@
+import includes from '../includes';
+
+describe('includes', () => {
+  test('should return true or false whether or not the object has the specified value', () => {
+    const obj = {
+      a: 1,
+      b: 2,
+    };
+
+    expect(includes(obj, 1)).toBe(true);
+    expect(includes(obj, 2)).toBe(true);
+    expect(includes(obj, 3)).toBe(false);
+  });
+
+  test('should check within deep objects with follow is true', () => {
+    const obj = {
+      a: 1,
+      b: {
+        c: {
+          d: 2,
+        },
+      },
+    };
+
+    expect(includes(obj, 2)).toBe(false);
+    expect(includes(obj, 2, {
+      follow: true,
+    })).toBe(true);
+  });
+
+  test('should throw TypeError for invalid arguments', () => {
+    const invalidObj: unknown = 'testing';
+    const invalidFollow: unknown = 'testing';
+
+    expect(() => includes(invalidObj as OObject, 'test'))
+      .toThrow(new TypeError('Expected Object, got string testing'));
+    expect(() => includes({}, 'test', {
+      follow: invalidFollow as boolean,
+    }))
+      .toThrow(new TypeError('Expected Boolean, got string testing'));
+  });
+});