test(core): isPlainObject covered with tests

Author: Reversean

packages/core/tests/utils/type-guards.test.ts

@@ -0,0 +1,18 @@
+import { describe, expect, it } from 'vitest';
+import { isPlainObject } from '../../src';
+
+class Foo {}
+const fooInstance = new Foo();
+
+describe('isPlainObject', () => {
+  it('should return true for plain object', () => expect(isPlainObject({})).toBe(true));
+  it('should return true for plain object with properties', () => expect(isPlainObject({ a: 1 })).toBe(true));
+  it('should return false for array', () => expect(isPlainObject([])).toBe(false));
+  it('should return false for string', () => expect(isPlainObject('x')).toBe(false));
+  it('should return false for number', () => expect(isPlainObject(42)).toBe(false));
+  it('should return false for boolean', () => expect(isPlainObject(true)).toBe(false));
+  it('should return false for null', () => expect(isPlainObject(null)).toBe(false));
+  it('should return false for undefined', () => expect(isPlainObject(undefined)).toBe(false));
+  it('should return false for class prototype', () => expect(isPlainObject(Foo)).toBe(false));
+  it('should return false for class instance', () => expect(isPlainObject(fooInstance)).toBe(false));
+});