Claude Code SDK Testing Workflow Guide

This guide provides practical steps and best practices to help you accomplish this task effectively. Follow the recommendations to get the best results from your AI tools.

Introduction

Testing is a critical aspect of SDK development, ensuring reliability, stability, and correct behavior across different use cases. This guide covers establishing testing workflows for Claude Code SDK implementations.

Setting Up Your Test Environment

Before writing tests, ensure your development environment is properly configured:

# Install dependencies
npm install --save-dev jest @testing-library/react vitest

# Install SDK dependencies
npm install @anthropic-ai/claude-code-sdk

Unit Testing Fundamentals

Unit tests form the foundation of your testing strategy. Focus on testing individual functions and methods in isolation:

// Example unit test for SDK client
import { ClaudeCodeClient } from '../src/client';

describe('ClaudeCodeClient', () => {
  let client: ClaudeCodeClient;

  beforeEach(() => {
    client = new ClaudeCodeClient({
      apiKey: process.env.CLAUDE_API_KEY
    });
  });

  it('should initialize with correct configuration', () => {
    expect(client.config.apiKey).toBeDefined();
    expect(client.config.maxTokens).toBe(4096);
  });

  it('should throw error when API key is missing', () => {
    expect(() => new ClaudeCodeClient({})).toThrow('API key is required');
  });
});

Integration Testing

Integration tests verify that your SDK works correctly with external services:

// Integration test example
import { ClaudeCodeClient } from '../src/client';

describe('Claude Code SDK Integration', () => {
  const client = new ClaudeCodeClient({
    apiKey: process.env.CLAUDE_API_KEY!
  });

  it('should successfully generate completion', async () => {
    const response = await client.completions.create({
      model: 'claude-3-sonnet',
      prompt: 'Write a hello world function',
      maxTokens: 100
    });

    expect(response.completion).toBeDefined();
    expect(response.completion.length).toBeGreaterThan(0);
  }, 30000);
});

Mock Testing Strategies

When testing without API access or to control responses, use mocking:

// Mock example using Jest
import { ClaudeCodeClient } from '../src/client';

jest.mock('../src/client');

const mockCompletion = {
  completion: 'function hello() { return "Hello World"; }',
  model: 'claude-3-sonnet',
  stopReason: 'stop_sequence'
};

describe('Mocked SDK Tests', () => {
  beforeEach(() => {
    jest.clearAllMocks();
  });

  it('should handle API errors gracefully', async () => {
    const client = new ClaudeCodeClient({
      apiKey: 'test-key'
    });

    client.completions.create = jest.fn()
      .mockRejectedValue(new Error('Rate limit exceeded'));

    await expect(client.completions.create({
      prompt: 'test',
      model: 'claude-3-sonnet',
      maxTokens: 100
    })).rejects.toThrow('Rate limit exceeded');
  });
});

End-to-End Testing

E2E tests validate complete user workflows:

// E2E test example
import { ClaudeCodeClient } from '../src/client';
import { TestRunner } from './test-runner';

describe('Complete SDK Workflow', () => {
  it('should complete full development workflow', async () => {
    const client = new ClaudeCodeClient({
      apiKey: process.env.CLAUDE_API_KEY!
    });

    // Step 1: Generate code
    const codeResponse = await client.completions.create({
      model: 'claude-3-sonnet',
      prompt: 'Create a simple calculator class in TypeScript',
      maxTokens: 500
    });

    // Step 2: Verify generated code
    expect(codeResponse.completion).toContain('class Calculator');

    // Step 3: Execute code (if applicable)
    const runner = new TestRunner();
    const result = runner.execute(codeResponse.completion);
    expect(result.success).toBe(true);
  });
});

Continuous Integration Setup

Automate your tests in CI/CD pipelines:

# GitHub Actions workflow
name: SDK Tests

on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'

      - name: Install dependencies
        run: npm ci

      - name: Run unit tests
        run: npm run test:unit

      - name: Run integration tests
        run: npm run test:integration
        env:
          CLAUDE_API_KEY: ${{ secrets.CLAUDE_API_KEY }}

Test Coverage Best Practices

Maintain high test coverage across your SDK:

Core functionality: 90%+ coverage for critical paths
Edge cases: Test error conditions, invalid inputs
API responses: Validate parsing and transformation logic
Configuration: Test all configuration options

Performance Testing

Ensure your SDK meets performance requirements:

// Performance test example
describe('Performance Tests', () => {
  it('should respond within 5 seconds', async () => {
    const start = Date.now();

    await client.completions.create({
      model: 'claude-3-sonnet',
      prompt: 'Hello',
      maxTokens: 10
    });

    const duration = Date.now() - start;
    expect(duration).toBeLessThan(5000);
  });
});

Structuring Your Test Suite for Long-Term Maintainability

As your SDK usage grows, disorganized tests become a liability. A well-structured test suite reduces maintenance burden and makes it easier to onboard new developers.

Group tests by behavior, not by method name. Instead of describe('completions.create'), write describe('when generating code with valid parameters'). This naming convention surfaces intent immediately and makes failures easier to diagnose.

Use a shared fixtures module to keep test data centralized. Duplicating mock responses across test files leads to inconsistencies when the API response shape changes:

// tests/fixtures/completions.ts
export const successfulCompletion = {
  completion: 'const add = (a: number, b: number) => a + b;',
  model: 'claude-3-sonnet',
  stopReason: 'stop_sequence',
  usage: { inputTokens: 12, outputTokens: 18 }
};

export const rateLimitError = new Error('Rate limit exceeded');
rateLimitError.name = 'ClaudeRateLimitError';

Apply the test pyramid principle. Aim for roughly 70% unit tests, 20% integration tests, and 10% E2E tests. Unit tests run in milliseconds; E2E tests against live APIs take seconds and cost tokens. Keeping this ratio ensures fast feedback loops without sacrificing confidence.

Handling Flaky Tests in SDK Workflows

SDK tests that hit real APIs introduce flakiness from network timeouts, rate limits, and non-deterministic model outputs. Address each category explicitly.

Rate limit flakiness: Add exponential backoff in your test retry configuration:

// jest.config.ts
export default {
  testTimeout: 30000,
  retryTimes: 2,       // jest-circus supports test-level retries
  retryDelay: 1000,
};

Non-deterministic output: For tests that verify generated code correctness, avoid asserting on exact string matches. Instead, test structural properties:

it('should return valid TypeScript', async () => {
  const response = await client.completions.create({
    model: 'claude-3-sonnet',
    prompt: 'Write a TypeScript function that adds two numbers',
    maxTokens: 200
  });

  // Structural checks instead of exact match
  expect(response.completion).toMatch(/function|const|=>/);
  expect(response.completion).toContain('number');
  expect(response.stopReason).toBe('stop_sequence');
});

Network timeouts: Set conservative timeouts per test and use mock servers for the bulk of your test runs. Reserve live API calls for a nightly integration suite that runs outside of PR checks.

Snapshot Testing for SDK Response Schemas

When your application depends on specific shapes of API responses, snapshot tests catch regressions from schema changes automatically.

// tests/snapshots/response-schema.test.ts
import { ClaudeCodeClient } from '../src/client';
import nock from 'nock';

describe('Response schema snapshots', () => {
  beforeEach(() => {
    nock('https://api.claude.ai')
      .post('/v1/completions')
      .reply(200, {
        completion: 'hello world',
        model: 'claude-3-sonnet',
        stopReason: 'stop_sequence',
        usage: { inputTokens: 5, outputTokens: 3 }
      });
  });

  it('completion response matches expected schema', async () => {
    const client = new ClaudeCodeClient({ apiKey: 'test' });
    const response = await client.completions.create({
      model: 'claude-3-sonnet',
      prompt: 'hello',
      maxTokens: 10
    });

    expect(response).toMatchSnapshot();
  });
});

Run jest --updateSnapshot when you intentionally update the response schema. Commit the updated snapshot file so reviewers can see exactly what changed. This pattern is especially useful when upgrading SDK versions — broken snapshots immediately surface breaking changes.

Testing Token Usage and Cost Controls

Production SDK integrations need safeguards against runaway token consumption. Test your cost control logic as a first-class concern:

describe('Token usage controls', () => {
  it('should reject requests that exceed token budget', async () => {
    const client = new ClaudeCodeClient({
      apiKey: process.env.CLAUDE_API_KEY!,
      maxTokensPerRequest: 500
    });

    await expect(client.completions.create({
      model: 'claude-3-sonnet',
      prompt: 'Write a complete REST API in TypeScript',
      maxTokens: 1000  // Exceeds the budget
    })).rejects.toThrow('Exceeds maximum tokens per request');
  });

  it('should track cumulative usage across requests', async () => {
    const client = new ClaudeCodeClient({ apiKey: 'test' });
    // Make multiple requests and verify usage tracking
    const usageBefore = client.getUsageStats().totalTokens;
    await client.completions.create({ model: 'claude-3-sonnet', prompt: 'hi', maxTokens: 10 });
    const usageAfter = client.getUsageStats().totalTokens;
    expect(usageAfter).toBeGreaterThan(usageBefore);
  });
});

Pair these tests with alerting in production to catch unexpected cost spikes early. A well-tested token management layer prevents the kind of billing surprises that turn small experiments into expensive incidents.

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