sanity checks

Guri Bee

3 min read

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21-10-2024

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Sanity Checks: The Unsung Heroes of Reliable Software

In the world of software development, meticulous attention to detail is crucial. A single overlooked error can snowball into significant problems, costing time, resources, and reputation. This is where sanity checks come in. They act as a safety net, ensuring the logic and data within your code are reasonable and prevent unexpected behavior.

But what exactly are sanity checks?

What are Sanity Checks?

Sanity checks are simple checks performed throughout your code to verify that data is within expected bounds and that your program is operating as intended. They are a form of defensive programming, aiming to catch errors early on and prevent them from propagating further.

Examples of Sanity Checks

Let's look at a few common examples:

• Validating User Input: Imagine you're building a form where users enter their age. A sanity check here would be to ensure the entered age is a positive number and within a reasonable range, say between 0 and 120. This prevents users from accidentally entering unrealistic data like negative ages or ridiculously high numbers.
• Array Bounds Checking: When working with arrays, a common sanity check is to verify that the index used to access an array element is within the valid range. Accessing an array element outside its bounds can lead to crashes or unpredictable behavior.
• Checking for Null Values: It's essential to verify that variables and objects are not null before attempting to use them. Attempting to access properties or call methods on a null object will result in an error.

How Sanity Checks Benefit You

• Early Error Detection: Sanity checks help you identify problems early in the development process, preventing them from becoming major issues later.
• Improved Code Reliability: By verifying data and logic, sanity checks ensure that your code behaves as expected, leading to more reliable and robust software.
• Reduced Debugging Time: Sanity checks can significantly reduce the time spent debugging code by pinpointing potential errors early on.

A Real-World Example from GitHub

Here's an example from a GitHub repository (https://github.com/facebook/react/blob/main/packages/react-dom/src/events/DOMEventProperties.js) that illustrates the use of sanity checks:

// This is a sanity check to make sure we're not accidentally using an invalid
// event name in the DOMEventProperties.js module.
// This should never happen, but we'd rather catch it in development than have
// it silently fail.

// To add a new event, do the following:
// 1. Update `DOMEventProperties.js` to include the event name.
// 2. Update this test by adding the event name in `EventNames` below.
// 3. If there is no code that uses the event name, then delete the event from
// `DOMEventProperties.js` and remove the test from `EventNames` below.

// It's important to note that this check will only work in development mode.
// In production mode, this check is stripped out, but we always want to be
// careful about using event names that don't exist.

const EventNames = [
  // ... (other event names)
];

if (__DEV__) {
  // Check for missing or invalid event names in EventNames.
  const invalidEventNames = Object.keys(DOMEventProperties).filter(
    (eventName) => !EventNames.includes(eventName),
  );

  if (invalidEventNames.length) {
    console.error(
      "Invalid event names: %s\n" +
        "Ensure that you have the correct names in EventNames array.",
      invalidEventNames.join(", "),
    );
  }
}

This code snippet ensures that the event names used in the React DOM are valid. This is a crucial sanity check that prevents potential errors and improves the overall stability of the React library.

Conclusion

Sanity checks are an integral part of robust software development. By incorporating these checks throughout your code, you can improve its reliability, reduce debugging time, and increase confidence in your software's performance.

Further Reading

• Defensive Programming
• Sanity Checks in Software Development
• Code Quality: Sanity Checks

Remember: Sanity checks are often overlooked but contribute significantly to building reliable and maintainable software. Make them a habit in your development workflow and watch your code quality soar!