Avro Payloads

Consumer Contract

{
  "type": "Asynchronous/Messages",
  "comments": {
    "references": {
      "AsyncAPI": { "operationId": "receiveUserSignedUp" }
    }
  },
  "contents": {
    "contentType": "avro/binary;record=com.example.UserSignedUp"
  }
}

Provider Contract

components:
  messages:
    UserSignedUp:
      contentType: avro/binary
      payload:
        schemaFormat: application/vnd.apache.avro;version=1.9.0
        schema:
          type: record
          name: UserSignedUp
          namespace: com.example
          fields:
            - name: userId
              type: string
            - name: email
              type: ["null", "string"]
              default: null

Value Check

Contract Testing decodes the consumer's example message and validates it against the provider's schema, in the same way as a JSON payload.

Structure Check

A change to an Avro schema can keep the example valid and still break the consumer. For example, if the provider changes a field from int to long, the consumer's decoder can no longer read the message. The structure check catches these changes.

The structure check uses Avro schema resolution. The writer encodes a message with its schema. The reader decodes it with its own schema and resolves the differences:

Which side is the writer depends on the interaction:

The structure check assumes that the reader decodes with the writer's schema, for example by looking it up in a schema registry. This is how Avro schema resolution works.

All fields in the consumer's schema are compared. If the consumer's schema is a projection that has only the fields the consumer uses, only those fields are compared. The consumer's example is used only to decide whether a default value or an enum symbol matters to the consumer.

Structure Check Rules

Errors are reported as message.payload.incompatible, and warnings as message.payload.risky. Where a rule applies, the result message ends with the rule name in parentheses.