Encryption is vital for modern applications, and Transport Layer Security (TLS) plays a key role in securing data by encrypting communications and verifying device identities. However, TLS certificates expire and need regular rotation to maintain security, as expired certificates can lead to service outages and vulnerabilities. Gremlin provides a solution to this challenge by enabling the testing of the entire TLS certificate chain for expiration through its Certificate Expiry experiment. This tool automates the detection of expiring certificates across all network-based services, ensuring organizations can proactively manage certificate validity. Gremlin's platform also creates a suite of reliability tests, including Certificate Expiry, which contributes to a service's overall reliability score. By automating these tests, organizations can avoid missing expiring certificates and can ensure their systems remain secure against potential impersonation attacks.