Method Verifier Reference

Created by should().method<R>(entry: ((...params: any[]) => R) | null | undefined). Both checks invoke the function with the arguments they are given and assert how the invocation ends.

Methods

Method	Role
`throws(...args)`	passes when invoking the function with `args` throws (inverted by a preceding `not`)
`returns(...args)`	invokes the function with `args`, asserts it does not throw, and returns the produced value for further chains

Plus the inherited not and defined().

Semantics

returns() under not asserts the invocation throws and yields undefined.
A null/undefined entry fails every check with The entry is not defined., regardless of not (see Concepts).
The thrown error itself is not inspected — any exception counts; assert on it separately when its shape matters.

Representative messages

The method didn't throw./The method did throw, but should not.
The method threw instead of returning./The method did return a value, but should not.

Guide: Methods.

16 September 2026