We’re using expect.js at work for our test assertions.
And today I learnt that you can have an assertion on whether an object has a key or not.
I needed to assert that an object was not saved with a certain key in our database.
So I was able to use expect(savedObject).to.not.have.key('dates') which was very handy!
Docs for expect.js: https://github.com/Automattic/expect.js