Agent-to-Agent Protocol Testing: How to Verify Your A2A Implementation

Testing an Agent2Agent (A2A) implementation requires separate checks for protocol conformance and real-world agent behavior, since an agent may satisfy the A2A wire contract while still producing inaccurate, unsafe, or policy-violating responses. Introduced by Google in 2025 and later hosted by the Linux Foundation, A2A version 1.0.0 defines public agent-card discovery, required card fields, task lifecycle states, authentication expectations, and JSON-RPC, gRPC, and HTTP+JSON transport bindings that must provide equivalent results when advertised. Recommended conformance tests include validating the agent card at the well-known endpoint, checking legal task transitions and distinctions such as rejected versus failed or auth-required, verifying declared streaming and push-notification capabilities, testing credential rejection, and comparing outputs across supported transports. The official pytest-based A2A Technology Compatibility Kit can automate many of these checks, particularly mandatory requirements, and produces CI-friendly reports. However, behavior evaluation must independently assess answer quality, hallucinations, privacy exposure, bias, escalation handling, and domain-specific risks through scenario-based testing against live endpoints. Teams can combine protocol and behavior suites in CI, running conformance first and using score thresholds for behavior, while taking care that evaluations against agents connected to production systems may trigger real external side effects.

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