Unit Testing a Custom Error Class in Node.js with Jest and Handling Edge Cases
I'm sure I'm missing something obvious here, but I'm trying to unit test a custom error class in my Node.js application that extends the built-in Error class. The class is designed to include an error code and additional context, but I'm running into issues when verifying its properties during testing. I have the following custom error class implementation: ```javascript class CustomError extends Error { constructor(message, code) { super(message); this.code = code; this.name = this.constructor.name; Error.captureStackTrace(this, this.constructor); } } ``` Now, I want to test this class to ensure it behaves as expected in various scenarios. Here's my test case: ```javascript const CustomError = require('./CustomError'); test('should create an instance of CustomError with correct properties', () => { const error = new CustomError('An error occurred', 'ERR_CUSTOM'); expect(error).toBeInstanceOf(CustomError); expect(error.message).toBe('An error occurred'); expect(error.code).toBe('ERR_CUSTOM'); expect(error.name).toBe('CustomError'); }); ``` While this test passes, I'm also concerned about edge cases, such as what happens if no error code is provided. I tried adding a check and a default value in the constructor: ```javascript constructor(message, code = 'UNKNOWN_ERROR') { super(message); this.code = code; this.name = this.constructor.name; Error.captureStackTrace(this, this.constructor); } ``` However, I want to ensure that if I omit the code argument, the default value is set correctly. I wrote this additional test: ```javascript test('should set default code if not provided', () => { const error = new CustomError('An error occurred'); expect(error.code).toBe('UNKNOWN_ERROR'); }); ``` This test works fine, but I'm curious about best practices for testing error classes. Should I also test the stack trace or am I over-engineering this? Additionally, I'm using Jest version 28.0.0 and wondering if there are any specific configurations or utilities in Jest that can help with testing custom errors. Any insights would be greatly appreciated! This issue appeared after updating to Javascript stable. Any ideas how to fix this? For context: I'm using Javascript on Linux. Any advice would be much appreciated.