testing-patterns

# Testing Patterns for Vercel AI SDK

**Purpose:** Provide comprehensive testing templates, mock providers, and testing strategies for Vercel AI SDK applications.

**Activation Triggers:**
- Writing tests for AI features
- Creating mock AI providers
- Testing streaming responses
- Testing tool calling functionality
- Implementing test coverage
- Snapshot testing for AI outputs

**Key Resources:**
- `templates/mock-provider.ts` - Mock language model implementation
- `templates/streaming-test.ts` - Test streaming responses
- `templates/tool-calling-test.ts` - Test tool execution
- `templates/snapshot-test.ts` - Snapshot testing for outputs
- `scripts/generate-test-suite.sh` - Generate test scaffolds
- `scripts/run-coverage.sh` - Run tests with coverage
- `examples/` - Complete test suites for different features

## Mock Provider Pattern

**Template:** `templates/mock-provider.ts`

```typescript
import { createMockLanguageModelV1 } from 'ai/test'

const mockProvider = createMockLanguageModelV1({
  doGenerate: async ({ prompt, mode }) => ({
    text: 'Mocked response'
    finishReason: 'stop'
    usage: { promptTokens: 10, completionTokens: 20 }
  })
  doStream: async function* ({ prompt, mode }) {
    yield { type: 'text-delta', textDelta: 'Mocked ' }
    yield { type: 'text-delta', textDelta: 'streaming ' }
    yield { type: 'text-delta', textDelta: 'response' }
    yield {
      type: 'finish'
      finishReason: 'stop'
      usage: { promptTokens: 10, completionTokens: 20 }
    }
  }
})
```

## Testing Strategies

### 1. Unit Tests (Mock Providers)

Test AI functions without real API calls

### 2. Integration Tests (Real Providers)

Test with real providers in CI (with rate limits)

### 3. Snapshot Tests

Ensure consistent outputs over time

### 4. E2E Tests

Test complete user flows with mocks

## Test Coverage Goals

- Core Functions: >90%
- Error Handling: >80%
- Tool Calling: 100%
- Streaming: >85%

## Resources

**Templates:**
- `mock-provider.ts` - Complete mo