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Testing LinkedListNode Implementation in javascript-algorithms

This test suite validates the core functionality of LinkedListNode implementation in a JavaScript data structures library. It covers node creation, value assignment, node linking, and string conversion capabilities.

Test Coverage Overview

The test suite provides comprehensive coverage of LinkedListNode operations:

Node initialization with primitive and object values
Node linking functionality verification
String conversion with default and custom stringifiers
Edge cases handling for different value types
Null reference handling for next pointers

Implementation Analysis

The testing approach utilizes Jest’s describe/it pattern for clear test organization. Each test case isolates specific node functionality using atomic assertions.

The implementation leverages Jest’s expect API with toBe, toBeNull, and toBeDefined matchers for precise state verification. Custom callback testing demonstrates advanced string conversion flexibility.

Technical Details

Testing Framework: Jest
Test Pattern: Unit Tests
File Structure: Modular test organization
Assertion Style: Expect API
Setup: Direct class import and instantiation

Best Practices Demonstrated

The test suite exemplifies several testing best practices including isolation of test cases, clear naming conventions, and comprehensive edge case coverage.

Single responsibility per test case
Descriptive test naming
Proper setup and teardown
Consistent assertion patterns
Modular test organization

trekhleb/javascript-algorithms

src/data-structures/linked-list/__test__/LinkedListNode.test.js

            
import LinkedListNode from '../LinkedListNode';

describe('LinkedListNode', () => {
  it('should create list node with value', () => {
    const node = new LinkedListNode(1);

    expect(node.value).toBe(1);
    expect(node.next).toBeNull();
  });

  it('should create list node with object as a value', () => {
    const nodeValue = { value: 1, key: 'test' };
    const node = new LinkedListNode(nodeValue);

    expect(node.value.value).toBe(1);
    expect(node.value.key).toBe('test');
    expect(node.next).toBeNull();
  });

  it('should link nodes together', () => {
    const node2 = new LinkedListNode(2);
    const node1 = new LinkedListNode(1, node2);

    expect(node1.next).toBeDefined();
    expect(node2.next).toBeNull();
    expect(node1.value).toBe(1);
    expect(node1.next.value).toBe(2);
  });

  it('should convert node to string', () => {
    const node = new LinkedListNode(1);

    expect(node.toString()).toBe('1');

    node.value = 'string value';
    expect(node.toString()).toBe('string value');
  });

  it('should convert node to string with custom stringifier', () => {
    const nodeValue = { value: 1, key: 'test' };
    const node = new LinkedListNode(nodeValue);
    const toStringCallback = (value) => `value: ${value.value}, key: ${value.key}`;

    expect(node.toString(toStringCallback)).toBe('value: 1, key: test');
  });
});