Allows to bypass chai's property assertions, which make linters unhappy (confer eslint/eslint#2102).

Provides the following functions, which is the appropriate property getters under the hood:

• beOk
• beTrue
• beFalse
• beNull
• beUndefined
• beEmpty
• beArguments
• toExist

Use them like this:

expect(object).toExist();
expect(array).to.beEmpty();

Sinon assertions are also supported, for example:

expect(spy).to.have.beenCalled();