To Assert or Not To Assert

Fri Feb 28 2025

Eric Thomas D. Cabigting

Assertions, what are they and why they are important. Are you using them?

An assertion is a statement or function in programming that checks if a condition is true. If the condition is true, the program continues running as expected. If the condition is false, the assertion typically throws an error or stops the program, indicating that something unexpected has happened.

How Do Assertions work?

Assertions are used to validate assumptions in your code. They act as a safety net to catch bugs, unexpected behavior, or invalid states. Here’s the basic flow:

• First, check a Condition: The assertion evaluates a condition (e.g., x === 5).
• Second, if True: The program continues running.
• Lastly, if False: The assertion throws an error or stops execution, signaling that something is wrong.

Here is an example in javascript

var expect = function(val) {
    this.toBe = function(value) {
        if(val === value) {
            return true;
        } else {
            throw "Not Equal";
        }
    };

    this.notToBe = function(value) {
        if(val === value) {
            throw "Equal";
        } else {
            return true;
        }
    };

    return this;
};

What does this function do?

• expect(val):
  • This is the main function that takes a vlue(val) as input.
  • It returns and object with two methods: toBe and notToBe.
• toBe(value):
  • This method checks if val is strictly equal (===) to the provided value.
  • If they are equal, it return true.
  • If they are not equal, it throws an error with the message "Not Equal".
• notToBe(value)
  • This method checks if val is not strictly not equal (===) to the provided value.
  • If they are not equal, it returns true.
  • If they are equal, it throws an error with the message "Equal"

Why Is This Useful?

This function is a simplified version of what testing libraries do. It helps you:

• Write Tests: You can use it to write custom test for your code.
• Debug: Quickly check if values match your expectations
• Learn: Understand how assertion libraries work under the hood.

So Should you use Assertions in your code?

Absolutely! It is a simple but powerful concept for comparing values and handling errors. It’s a way to explicitly check if a condition is true during the execution of a program. If the condition is false, the program typically throws an error or stops execution to indicate that something unexpected has happened.