Scaling an OTP test should mean increasing confidence in the flow, not sending as many messages as possible. Begin with an agreed test environment, a traffic budget and synthetic accounts.
Separate correctness from capacity
First test whether a code works for the intended account and purpose, expires according to policy and handles repeated or incorrect entry correctly. A capacity test is a separate exercise that needs authorization, monitoring and a stop condition.
Use a focused correctness matrix
- Correct code entered within its validity window.
- Incorrect code entered within the application's attempt policy.
- Correct code entered after expiry.
- Code reused after a successful action.
- Earlier code entered after a resend.
- Code presented for a different synthetic account.
Correlate each message
Associate the recipient and request time with the test run. Do not take the newest email in a shared inbox without checking its purpose. Delayed messages from earlier runs can otherwise produce false results.
Control the load
Limit simultaneous runs, use bounded waiting and respect API retry guidance. Stop when the receiving or sending system shows sustained errors. Do not test a third-party service's limits by repeatedly creating accounts or requesting verification messages.
Keep reports free of usable codes
Store pass/fail state, sanitized identifiers and stage timings rather than OTP values or raw email bodies. Delete synthetic account data under the agreed test policy. A single receiving provider's result does not measure delivery to every production mailbox.