Playwright API Mocking and Specmatic: When and Why to Use Each 

Playwright API mocking is a test-level capability designed to stub network calls within browser-based UI tests. 

Specmatic is a contract-driven API contract testing, simulation and validation platform designed to ensure API correctness, realism, and governance across teams, tools, and environments. 

Core Philosophy Difference 

What Playwright API Mocking Is Best At 

Playwright API mocking excels when teams need: 

• Fast, localised, ah-hoc stubbing of backend calls 

• Deterministic UI tests without backend dependencies 

• Simple simulation of success or failure paths 

• Tight integration within Playwright-based test suites 

It is intentionally lightweight and tester-centric, making it ideal for UI-focused test scenarios. 

What Specmatic Is Designed For 

While Specmatic can certainly help with mocking backend API call for designing deterministic UI tests, but it also addresses challenges that emerge as systems and organisations scale: 

• APIs used by multiple consumers (web, mobile, partners) 

• Parallel development across frontend, backend, and integration teams 

• Need for realistic mocks that don’t drift from production behaviour 

• Early detection of API breaking changes 

• Governance, standardisation, and resilience testing 

Specmatic uses API specifications as the single source of truth, ensuring all simulations and validations remain aligned with real API expectations. 

Key Capability Differences 

Why This Difference Matters at Scale 

As systems grow, teams often face UI tests passing locally while in staging or production functionality break, inconsistent assumptions between teams, late discovery of breaking changes, and incomplete edge-case testing. Specmatic shifts API correctness earlier in the lifecycle. 

Playwright API Mocking vs Specmatic — Detailed Difference

When to Choose Which Tool

• Use Playwright API Mocking for quick UI stubs and simple API behaviour.
• Use Specmatic when APIs are shared, correctness matters, and governance is required. 

Summary 

Playwright API mocking is a test-level optimisation tool. 

Specmatic is a contract-driven platform for API simulation, validation, and governance. It enables fast UI testing without sacrificing API correctness or realism.