Analyze and improve Terraform provider test coverage using terraform-plugin-testing v1.13.3+ patterns. Use when (1) analyzing test coverage gaps, (2) adding missing tests (drift detection, import, idempotency), (3) converting legacy patterns to modern state checks, (4) tracking optional field coverage, (5) verifying test quality, or (6) validating example accuracy. Supports automated coverage analysis, guided pattern improvements, and example testing.