Contract Test Design

When to Use This Skill

Use this skill when:

• Contract Test Design tasks - Working on consumer-driven contract testing strategies using Pact

• Planning or design - Need guidance on contract testing approaches

• Best practices - Want to follow established patterns and standards

Overview

Contract testing verifies that services communicate correctly by testing the contract (API agreement) between a consumer and provider. Consumer-driven contracts (CDC) ensure providers don't break their consumers.

Contract Testing vs Other Test Types

Aspect E2E Tests Integration Tests Contract Tests

Scope Full system Component + deps Consumer-provider

Speed Slow (minutes) Medium (seconds) Fast (ms)

Reliability Often flaky Moderate Very stable

Deployment coupling High Medium Low (async)

Failure localization Poor Moderate Excellent

Maintenance High Medium Low

Consumer-Driven Contract Flow

┌─────────────────────────────────────────────────────────────┐ │ CONSUMER SIDE │ │ │ │ 1. Consumer writes test 2. Test generates contract │ │ ┌──────────────┐ ┌──────────────┐ │ │ │ Consumer │ │ Contract │ │ │ │ Test │ ─────► │ (JSON) │ │ │ └──────────────┘ └──────────────┘ │ │ │ │ └──────────────────────────────────────┼──────────────────────┘ │ ▼ Publish to Broker ┌──────────────────┐ │ Contract Broker │ │ (Pact Broker) │ └────────┬─────────┘ │ ┌──────────────────────────────────────┼──────────────────────┐ │ PROVIDER SIDE │ │ │ ▼ │ │ 3. Provider verifies contract │ │ ┌──────────────┐ ┌──────────────┐ │ │ │ Provider │ ◄───── │ Contract │ │ │ │ Verification│ │ (JSON) │ │ │ └──────────────┘ └──────────────┘ │ │ │ │ │ ▼ │ │ 4. Provider tests pass = Contract honored │ │ │ └─────────────────────────────────────────────────────────────┘

Quick Reference: Breaking Changes

Change Type Breaking? Action

Remove field Yes Block deployment

Change field type Yes Block deployment

Add required field Yes Block deployment

Add optional field No Allow

Add new endpoint No Allow

Tooling Selection

Purpose Tool Rationale

Contract Framework PactNet .NET native, mature

Broker Pact Broker Standard, free tier

Async Contracts Pact Message Same ecosystem

Schema Validation OpenAPI Industry standard

References

Reference Content When to Load

strategy-template.md Contract testing strategy template, service maps, workflows Planning contract testing strategy

pact-dotnet-implementation.md Consumer tests, provider verification, provider states Implementing Pact in .NET

message-contracts.md Async message/event contract testing Testing event-driven architectures

matchers-cicd.md Pact matchers, breaking change detection, CI/CD pipelines Matcher syntax, CI/CD integration

Integration Points

Inputs from:

• API specifications → Contract definitions

• Service architecture → Consumer-provider map

• test-strategy-planning skill → Contract test scope

Outputs to:

• CI/CD pipeline → Contract verification gates

• API governance → Breaking change detection

• api-design-fundamentals skill → Contract-first design

Test Scenarios

Scenario 1: Planning contract testing strategy

Query: "Help me design a contract testing strategy for our microservices"

Expected: Skill activates, provides strategy template, guides through service mapping

Scenario 2: Implementing Pact tests

Query: "Show me how to write Pact consumer tests in .NET"

Expected: Skill activates, loads pact-dotnet-implementation.md reference, provides code examples

Scenario 3: CI/CD integration

Query: "How do I integrate contract testing into our GitHub Actions pipeline?"

Expected: Skill activates, loads matchers-cicd.md reference, provides pipeline examples

Last Updated: 2025-12-28

Version History

• v1.1.0 (2025-12-28): Refactored to progressive disclosure - extracted implementation to references/

• v1.0.0 (2025-12-26): Initial release