Placing a test order says "Test order limit reached (10)". How do I place more?

A store can hold at most 10 test orders at a time. Clear the old ones to place more:

1. Go to Orders → Manage Orders and click Filters.
2. Tick Show test orders.
3. Click Purge test orders and confirm with Purge.

This permanently deletes all test orders for your store and frees the limit. Real orders are not affected. Then click Place Test Order again to open your storefront in test mode.