Test migration to jest by hand

Apparently using regular expressions is way easier.

test/isPlainObject/isPlainObject.test.js

@@ -0,0 +1,11 @@
+const expect = require('expect');
+const isPlainObject = require('./isPlainObject.js');
+
+
+  test('isPlainObject is a Function', () => {
+  expect(isPlainObject).toBeInstanceOf(Function);
+});
+  t.equal(isPlainObject({ a: 1 }), true, 'Returns true for a plain object');
+  t.equal(isPlainObject(new Map()), false, 'Returns false for a Map (example of non-plain object)');
+  
+