Test A2A agents

An A2A agent (Agent2Agent protocol) is an agent other agents ask for work. It publishes a card that says what it does and how to reach it, and it answers a message with a reply or a task: work that goes through states (working, input required, completed…) and ends with artifacts. The a2a pack tests your agent by doing what another agent does.

Scenario: A hold asks until which day, and holds the parcel on the reply
  Given a seeds/a2a-hold.yaml db seed
  And the parcels a2a agent with the following properties:
    | url | http://localhost:8400 |
  When a message is sent to the parcels a2a agent:
    """
    Please hold PX-A2A-9202 at its depot.
    """
  Then the parcels a2a agent's task is input-required
  And the parcels a2a agent's answer contains 'Until which day should PX-A2A-9202 be held?'
  When a reply is sent to the parcels a2a agent:
    """
    2026-10-05
    """
  Then the parcels a2a agent's task is completed

Add the pack to the project with axx pack add a2a (Choose packs).

Register the agent

Property	What it is
url	The agent’s URL. Its card is read at /.well-known/agent-card.json on its origin.
card	The agent’s card, when it is not there: a file of the project, or a URL.
transport	How to reach the agent: JSONRPC, HTTP+JSON or GRPC, among the interfaces its card lists. Default: the card’s first.
header.<name>	A header sent with every request, such as header.Authorization.
timeout	How long a call may take. Default 30s.
push url, push token	Where the agent sends its tasks’ updates (a webhook: a WireMock the mock pack checks), and the token it sends with them.

The card is checked for what A2A 1.0 requires: its name, description, version, interfaces and input and output modes. Check what it says, and its skills:

Then the parcels a2a agent's card has the following properties:
  | name                   | Parcels agent |
  | capabilities.streaming | true          |
And the parcels a2a agent has the track-parcel skill

Send messages

When a message is sent to the parcels a2a agent:
  """
  Where is PX-A2A-9201?
  """
When the a2a/hold-request.json message is sent to the parcels a2a agent
When a reply is sent to the parcels a2a agent:
  """
  2026-10-05
  """
When the parcels a2a agent is asked to cancel its task

• A message starts a conversation, and waits for the agent’s answer: a reply, or a task that ended or waits for input.
• A reply continues the agent’s last task. That is how a task that asks for input (input-required) gets it.
• A file’s message is an A2A message in JSON, with text, data or file parts.

Check the answer

Then the parcels a2a agent's task is completed
And the parcels a2a agent's answer contains 'PX-A2A-9201 is in transit'
And the parcels a2a agent's task has an artifact where:
  | name        | parcel-status |
  | data.status | IN_TRANSIT    |

• States are written as people say them: submitted, working, completed, input-required, auth-required, failed, canceled and rejected. A check waits for a task still at work (10 seconds, or within {duration}), and fails at once for a task in another state that will not change without a message.
• The answer is the agent’s reply, or its task’s status message and the text of its artifacts.
• An artifact’s properties are its name, description, text (its text parts), data (its first data part: data.status) and parts.

Streams

When a message is streamed to the parcels a2a agent:
  """
  Where is PX-A2A-9204?
  """
Then the parcels a2a agent's stream received an update where:
  | kind    | status                 |
  | state   | working                |
  | message | Looking up PX-A2A-9204 |
And within 10s the parcels a2a agent's task is completed

A streamed message takes the agent’s answer as it comes: a status update has kind status, its state and its message; an artifact update has kind artifact and its artifact (artifact.name, artifact.data.status…). The checks wait for what the stream has not sent yet, and fail at once when it has ended. A stream belongs to the scenario, which ends it when it ends.

Mock the agents your service asks

When your service asks another team’s agent, the Axx WireMock image mocks it from its card, with a mapping file per answer, and the mock pack checks what your service asked it. See Mock MCP servers and A2A agents.

See the a2a pack’s reference for every step.