My app sends transactional email (signup confirmations, password resets, receipts, notifications) and I want tests proving the right emails go out, without sending real email. First, find every place my app sends email and list the triggers: what user action or system event causes each email. Then set up an email interception layer for tests that: 1. Captures outbound email instead of sending it, recording recipient, subject, and body. 2. Works regardless of which email provider or library my app uses. 3. Lets a test inspect the captured messages and clear the outbox between tests. Write tests for each email trigger asserting: the email goes to the correct recipient, the subject and key body content are right (including any links, tokens, or amounts), and no email is sent when the triggering condition fails (for example, no receipt email when a payment fails). Also check for the classic mistake: emails that contain broken links because of missing or hardcoded base URLs. Flag any email whose links point at localhost or a placeholder domain. When finished, run the suite and summarize which email flows are verified and which ones have no coverage.