3.2The Pact Workflow

+--------------+         +--------------+         +--------------+
|   CONSUMER   |         |  PACT BROKER |         |   PROVIDER   |
|  (Service A) |         |  (Registry)  |         |  (Service B) |
|              |         |              |         |              |
|  1. Write    |--pact-->|  2. Store    |--pact-->|  3. Verify   |
|     consumer |  file   |     contract |  file   |     provider |
|     test     |         |              |         |     test     |
+--------------+         +--------------+         +--------------+

Step 1: Consumer Writes Tests

The consumer team writes tests that describe what they expect from the provider. These tests run against a Pact mock server, not the real provider.

Step 2: Pact Broker Stores Contracts

The generated Pact file (a JSON contract) is published to a central broker. The broker stores all consumer contracts and tracks which versions are compatible.

Step 3: Provider Verifies

The provider team runs verification tests that replay the consumer's expectations against the real provider implementation. If any expectation fails, the provider knows they would break a consumer.