Simplifying Unit Testing Standalone Components

Demonstrate the advantages of testing standalone components which do not require the context of an entire module, making unit tests simpler and faster to run.

// A simple calculator component for demonstration
function Calculator() {
    // Method to add two numbers
    this.add = function (a, b) {
        return a + b;
    };
    // Method to subtract two numbers
    this.subtract = function (a, b) {
        return a - b;
    };
}

This is the standalone Calculator component with add and subtract methods, which can be easily unit tested without any external dependencies.

// Unit tests for the Calculator component using a basic testing framework (e.g., Jest)
describe('Calculator', () => {
    let calculator;
    // Setup the Calculator object before each test
    beforeEach(() => {
        calculator = new Calculator();
    });
    // Test the 'add' method
    test('adds 1 + 2 to equal 3', () => {
        expect(calculator.add(1, 2)).toBe(3);
    });
    // Test the 'subtract' method
    test('subtracts 2 - 1 to equal 1', () => {
        expect(calculator.subtract(2, 1)).toBe(1);
    });
});

The unit tests for the Calculator component, testing both the add and subtract methods in isolation. Using Jest test framework syntax for demonstration.