Case Study:
How TMForum Automated Their API Factory

A Technical Deep Dive into Real-World Contract Driven Development

Impact Snapshot: Hard Numbers and Real Results

100+ APIs standardized and automated

End-to-end validation of API specifications

Automated Conformance Tool Kit (CTK) and Virtual Service (VS) generation

Unified tooling across OpenAPI specs for REST and AsyncAPI specs for Kafka

The Mission: A Complete Overhaul to Consistently Deliver at Speed and Scale

Here’s something you don’t see every day: A complete overhaul of API management that actually delivered. TMForum wasn’t just dealing with a handful of APIs—we’re talking about an API Factory managing over 100 APIs in the telecommunications domain. 

The Real Challenge

When you’re working at this scale, good enough isn’t good enough. TMForum needed to: 

  • Ensure consistent implementation across multiple vendors 
  • Validate conformance efficiently
  • Keep specifications, testing tools, and reference implementations in sync
  • 10x the Developer Experience (make it developer-friendly)

But here’s the kicker: They needed to do this while improving adoption rates and reducing the time to release new APIs from months to days.

The Solution: Contract Driven Development in Action

TMForum implemented Contract Driven Development (CDD) using Specmatic, but they didn’t just stop at basic testing.

They built what they call the “API Forge”—a unified, fully automated API Factory that handles:

Specification Management

  • Single source of truth for API contracts
  • Automated generation and validation of examples
  • Synchronized tooling between OpenAPIs and AsyncAPIs

Development Pipeline

  • Automated generation of API artifacts
  • Interactive CLI for rapid development
  • Integration with CI as part of the PR process 

The Methodology: A Systematic Playbook for
Real-World Success

Let’s get into the nuts and bolts. TMForum’s implementation of Contract Driven Development wasn’t just about throwing tools at the problem.

We built a systematic approach that actually works in the real world.

CONTRACT DEFINITION (The Foundation)

  • Automated generation of OpenAPI and AsyncAPI specs as the single source of truth
  • Examples generated and validated against the contract
  • No more “it works on my machine” syndrome
  • Automated validation before anything hits production

AUTOMATED TOOLCHAIN (The Engine)

  • CTK generation straight from the specs
  • Virtual Service spun up automatically
  • User guides and Postman collections are just a click away
  • End-to-end testing of the tooling using Teswiz including visual validation with Applitools Eyes
  • Interactive CLI for rapid development

DEVELOPER EXPERIENCE (The Game Changer)

  • Local testing environment matches production
  • Immediate feedback on spec changes
  • Docker containers for consistent environments
  • GitHub Actions integration for CI/CD

QUALITY ASSURANCE (The Proof)

  • Every request/response pair validated
  • Error scenarios tested automatically
  • Edge cases covered systematically
  • Automated testing of the tooling including visual regression

Real-World Impact: Success Criteria that Prove the Difference

DEVELOPMENT VELOCITY

  • API release cycle: Months → Days
  • CTK creation: Manual process → Automated
  • Testing: Spotty coverage → Comprehensive validation

QUALITY METRICS

  • Spec compliance: Verified automatically
  • Error handling: Systematically tested
  • Edge cases: Identified and validated

MAINTENANCE EFFICIENCY

  • Single source of truth
  • Automated synchronization
  • Self-documenting processes

The Async Evolution: Extending to Event-Driven Architectures

But wait, there’s more (and this is actually important). TMForum didn’t stop at REST APIs. They extended the entire framework to handle AsyncAPIs, proving this approach scales across different architectural patterns.

The async implementation includes:

  • Event-driven architecture support
  • Kafka integration (with more protocols coming)
  • Both event and command pattern support
  • Automated testing for asynchronous flows

Achieving Real-World Impact with TMForum's API Factory

Your Next Moves: Get Started Today

If you’re managing APIs at scale, here’s your action plan: 

START SMALL

  • Pick one API that’s giving you trouble
  • Download Specmatic (it’s open source)
  • Follow the quick start guide at specmatic.io
  • See results in your first day

SCALE SMART

  • Use Docker containers for consistency
  • Integrate with your CI/CD pipeline
  • Implement visual testing for UI components
  • Automate everything that can be automated

GET SUPPORT

The Bottom Line: TM Forum is revolutionising the Telco Industry with Specmatic's Contract Driven Development

TMForum proved something important here: You can automate API testing and development without sacrificing speed, quality or control. They’re handling 100+ APIs with this setup. You can start with just one. 

Stop hoping your APIs work. With Specmatic make them work.

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This isn’t just another tool – it’s a proven approach to API lifecycle management that actually works in the real world. The code is open source for OpenAPI, the documentation is solid, and the community is there to help. 

Your move. 

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