const expect = require('expect'); const functions = require('./functions.js'); test('functions is a Function', () => { expect(functions).toBeInstanceOf(Function); }); function Foo() { this.a = () => 1; this.b = () => 2; } Foo.prototype.c = () => 3; t.deepEqual(functions(new Foo()), ['a', 'b'], 'Returns own methods'); t.deepEqual(functions(new Foo(), true), ['a', 'b', 'c'], 'Returns own and inherited methods');