What are the differences between describe, test, and it functions in Jest? How to use them to organize test code?

In Jest, describe, test, and it are all functions used to organize test code:

describe function:

• Used to group related test cases into test suites
• Accepts two parameters: a description string and a callback function
• Can be nested to create hierarchical structures
• Example: describe('User module', () => { ... })

test function:

• Defines a single test case
• Is an alias for it, both have identical functionality
• Accepts two parameters: a description string and a test function
• Example: test('should return user name', () => { ... })

it function:

• Has exactly the same functionality as test, it's an alias
• Using it makes test code read more like natural language
• Example: it('should return user name', () => { ... })

Usage Example:

javascript
describe('Calculator', () => {
  describe('addition', () => {
    test('should add two positive numbers', () => {
      expect(add(2, 3)).toBe(5);
    });
    
    it('should handle negative numbers', () => {
      expect(add(-2, 3)).toBe(1);
    });
  });
});

Best Practices:

• Use describe to logically group related tests
• Test descriptions should clearly express test intent
• Keep each test case with a single responsibility