When creating a mock object in unit testing, you typically expect its methods to behave in a simplified or controlled manner. Mock objects are used to simulate the behavior of real objects for testing purposes, so their methods should provide predictable responses that help you test specific scenarios. Options (1) and (4) are not typical expectations for mock methods. Option (2) would render the mock object useless for testing.

To destructure nested properties in JavaScript objects, you should use the syntax in Option 2. It allows you to access nested properties within myObject. The other options either contain incorrect syntax or won't work for this purpose.

Custom middleware is implemented in Express.js when you have specific application logic that cannot be handled by built-in middleware. Common scenarios include authentication, request logging, data validation, and handling application-specific errors. Built-in middleware covers common use cases, but custom middleware allows you to tailor the middleware pipeline to your application's unique needs.

The output of the code snippet is true. In JavaScript, the == operator performs type coercion, so it converts the string '1' to a number before comparing, and 1 is equal to 1.

The primary use of Streams in Node.js is for handling data in a streaming fashion, especially for reading and writing data efficiently. They are commonly used for handling HTTP requests and responses, file I/O, and more, where data can be processed in smaller chunks without loading the entire dataset into memory.

Normalizing database tables often improves Read performance by reducing data redundancy. However, it may complicate Update operations since data may be spread across multiple tables, requiring joins. Option 2 is not generally true as normalization tends to have a positive impact on Update operations. Option 4 is an oversimplification.

The resolve function in a JavaScript Promise is called when the Promise is fulfilled successfully with a value. It signifies that the asynchronous operation inside the Promise has completed successfully, and the value provided in the resolve function is the result.

A package can be listed in both dependencies and devDependencies when it's a development tool that is needed during both development and runtime. An example might be a testing library or build tool.

In Express.js, you can handle errors occurring in asynchronous code within a route handler by calling next(error). This passes the error to the error-handling middleware or the default error handler, allowing you to centralize error handling. Using a try-catch block won't catch asynchronous errors, and the other options are not standard practices for error handling in Express.js.

Unit Testing focuses on verifying the functionality of individual components (or units) in isolation. It helps ensure that each component works correctly on its own.