Yep, TypeScript has tests. Quite a lot, with a few different techniques:

• Unit Tests
• Baselines
• Fourslash

You run tests via gulp runtests.

Flags worth knowing:

• --failed - re-runs the failed tests only
• --no-lint - don't run the linter when it completes
• -i - Use the inspector to debug

If you have a fail in the baselines:

• gulp diff - to see the differences
• gulp baseline-accept to overwrite the current baseline snapshots