Question 1

How do I set up Unexpected with Jest?

Accepted Answer

Install Unexpected via npm and use it in Jest test files by requiring it and configuring Jest to use Unexpected's expect function. Since Jest supports custom assertion libraries, you might need to adjust settings or use a wrapper to integrate smoothly.

Question 2

Unexpected vs Chai: which is better for BDD testing?

Accepted Answer

Unexpected offers more expressive, natural language syntax and superior error diffs, enhancing test readability. Chai has a larger ecosystem and wider adoption, so choose Unexpected for clarity and extensibility, or Chai for community support and integrations.

Question 3

Does Unexpected work well with TypeScript?

Accepted Answer

Unexpected is written in JavaScript and can be used with TypeScript, but official type definitions might be limited. Check community repositories for third-party TypeScript support, as it may not be as seamless as with libraries like Jest.

Question 4

How can I create custom matchers in Unexpected?

Accepted Answer

Extend Unexpected by defining custom assertions using its plugin API: create a matcher with a name and implementation function, then register it via addAssertion to tailor the library for domain-specific testing needs.

Question 5

Is Unexpected good for testing asynchronous code?

Accepted Answer

Yes, Unexpected has built-in support for promises and async/await, allowing you to write assertions that handle asynchronous operations naturally, as mentioned in its features for comprehensive testing.

Question 6

What are the performance implications of using Unexpected?

Accepted Answer

Unexpected's detailed error diffing and expressive syntax might introduce slight overhead compared to minimal assertion libraries, but for most test suites, the impact is negligible, and the readability benefits often outweigh performance concerns.

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