Make an assertion, error will be thrown if expr does not have truthy value.

Make an assertion that actual and expected are equal, deeply. If not deeply equal, then throw.

Make an assertion that actual and expected are not equal, deeply. If not then throw.

Executes a function, expecting it to throw. If it does not, then it throws. An error class and a string that should be included in the error message can also be asserted. Or you can pass a callback which will be passed the error, usually to apply some custom assertions on it.