Create testing.mdx based on issue #267

Author: kgowru

fern/products/sdks/overview/typescript/testing.mdx

@@ -0,0 +1,97 @@
+---
+title: "Integration Tests"
+description: "Test your SDK with auto-generated integration tests"
+---
+
+# Integration Tests
+
+Fern can automatically generate integration tests for your TypeScript SDK to verify that your client behaves correctly against a mock server. This feature helps ensure your SDK works as expected and maintains compatibility with your API specification.
+
+## Supported Generators
+
+Integration test generation is currently supported in:
+- TypeScript SDK Generator (v1.2.4+)
+- C# SDK Generator
+
+<Callout type="info">
+We recommend using TypeScript SDK Generator v1.5.0 or later for the best experience with integration tests.
+</Callout>
+
+## Getting Started
+
+### Prerequisites
+
+- Fern CLI (latest version)
+- Node.js 16+
+- npm or yarn
+- TypeScript SDK Generator v1.2.4 or later
+
+### Updating Your Generator Version
+
+To use integration tests, ensure you're using a supported generator version:
+
+```yaml
+generators:
+  - name: fernapi/fern-typescript-sdk
+    version: 1.5.0
+    output:
+      location: local-file-system
+      path: ../generated/typescript
+```
+
+<Callout type="warning">
+If you're seeing version 1.0.0 or 1.0.1 selected automatically, update your Fern CLI to the latest version to access newer generator versions.
+</Callout>
+
+## Test Structure
+
+When you generate your SDK, Fern automatically creates:
+1. A test directory with the basic test infrastructure
+2. Integration tests based on your API specification
+3. Stubs for custom tests
+
+The generated tests use a mock server to validate:
+- Request/response handling
+- Parameter serialization
+- Error scenarios
+- Authentication flows
+- API endpoint behavior
+
+## Running Tests
+
+To run the integration tests:
+
+```bash
+npm test
+```
+
+Or with yarn:
+
+```bash
+yarn test
+```
+
+## Custom Tests
+
+While the auto-generated tests cover most common scenarios, you can add custom tests for specific use cases:
+
+```typescript
+describe('Custom API Tests', () => {
+  it('should handle specific business logic', async () => {
+    const client = new YourApiClient();
+    const response = await client.someEndpoint();
+    expect(response).toBeDefined();
+  });
+});
+```
+
+## Best Practices
+
+1. Keep your generator version up to date for the latest testing features
+2. Run tests before publishing SDK updates
+3. Add custom tests for complex business logic
+4. Use the mock server for consistent test behavior
+
+<Callout type="info">
+Integration test support for additional SDK generators is under development. Check the Fern documentation for updates.
+</Callout>