The first function to combine.
The second function to combine.
Optionaloptions: Options<Fn>A function to assert the equality of the two function results. (optional) defaults to deep equality check with JSON.stringify
A function to call when the two functions produce different results. (optional) defaults to logging error to console
A new function that combines the behavior of the two input functions.
Combines two functions into one, asserting that they produce the same result.