Squashed commit of the following:

commit 6a604d6
Author: Anthony Drendel <me@anthonydrendel.com>
Date:   Mon Apr 6 14:13:42 2026 +0200

    Manually fix IntegrationTesting project file

commit 3dbc207
Author: Anthony Drendel <atdrendel@users.noreply.github.com>
Date:   Mon Apr 6 12:56:23 2026 +0200

    Update IntegrationTesting/IntegrationTesting.xcodeproj/project.pbxproj

    Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

commit 21a0ab0
Author: Anthony Drendel <me@anthonydrendel.com>
Date:   Sun Apr 5 18:12:02 2026 +0200

    Add IntegrationTesting Xcode project and remove MLXLMIntegrationTests

commit 39cd9fc
Author: Anthony Drendel <me@anthonydrendel.com>
Date:   Sat Apr 4 15:07:28 2026 +0200

    Update documentation

commit 6d3fafa
Author: Anthony Drendel <me@anthonydrendel.com>
Date:   Sat Apr 4 14:58:38 2026 +0200

    Add MLXLMIntegrationTests

commit 89de43c
Author: Anthony Drendel <me@anthonydrendel.com>
Date:   Fri Apr 3 12:05:24 2026 +0200

    Add Mistral3, Nemotron, and Qwen3.5 tool call integration test helpers

Author: atdrendel

CONTRIBUTING.md

@@ -14,11 +14,43 @@ possible.
    You can also run the formatters manually as follows:
 
      ```
-     swift-format format --in-place --recursive Libraries Tools Applications
+     swift-format format --in-place --recursive Libraries Tools Applications IntegrationTesting
      ```
  
    or run `pre-commit run --all-files` to check all files in the repo.
  
+## Running Tests
+
+Unit tests run without any special hardware and do not download models:
+
+```
+swift test
+```
+
+Integration tests verify end-to-end model loading and generation. They require
+macOS with Metal and download models from Hugging Face Hub on first run. These
+tests do not run in CI.
+
+Open `IntegrationTesting/IntegrationTesting.xcodeproj` in Xcode and run the
+test target (`Cmd+U` or via the Test Navigator), or use `xcodebuild`:
+
+```bash
+# Run all integration tests
+xcodebuild test \
+  -project IntegrationTesting/IntegrationTesting.xcodeproj \
+  -scheme IntegrationTesting \
+  -destination 'platform=macOS'
+
+# Run a single test
+xcodebuild test \
+  -project IntegrationTesting/IntegrationTesting.xcodeproj \
+  -scheme IntegrationTesting \
+  -destination 'platform=macOS' \
+  -only-testing:IntegrationTestingTests/ToolCallIntegrationTests/qwen35FormatAutoDetection\(\)
+```
+
+See [Libraries/IntegrationTestHelpers/README.md](Libraries/IntegrationTestHelpers/README.md) for more details.
+
 ## Issues
 
 We use GitHub issues to track public bugs. Please ensure your description is