Senior QA / Test Engineer – API & Integration Migration

Summary

We are looking for a senior QA / Test Engineer to lead quality assurance across a large-scale API and integration platform migration.

The role focuses on proving that migrated integrations maintain functional parity with the existing implementation, meet required performance levels, and do not negatively affect non-migrated APIs or dependent systems.

You will own the test approach, API and integration test suites, performance testing, regression coverage, UAT execution, and quality sign-off before production cutovers. The position requires deep experience in API testing, strong performance-testing capabilities, and the ability to work independently as the quality gate for complex enterprise integrations.

Key Responsibilities

• Define and maintain the overall test strategy for API and integration migration activities.
• Design and execute functional, integration, parity, regression, end-to-end, and performance tests.
• Validate that migrated APIs provide functionally equivalent behavior to the existing implementation.
• Own and maintain API test suites across Development, UAT, and Production-oriented environments.
• Establish automated API testing using Postman / Newman and programmatic testing tools where required.
• Integrate automated tests into CI/CD pipelines.
• Execute and evaluate performance and load tests against production-like traffic conditions.
• Design regression coverage to ensure that migrated changes do not affect other APIs or integrations.
• Coordinate test data and ensure appropriate coverage of standard, boundary, and error scenarios.
• Own UAT execution and sign-off, providing clear evidence for production-readiness decisions.
• Work closely with Integration Developers, Technical Leads, platform specialists, and DevOps throughout the delivery lifecycle.
• Support smoke testing and validation during production cutovers.

Required Experience

• 5+ years of experience in API integration testing.
• Previous experience testing an API migration, re-platforming, or parallel implementation, where functional parity between two implementations had to be demonstrated.
• Strong hands-on experience with Postman and Newman.
• Experience creating automated or programmatic API tests using tools such as RestAssured, pytest-requests, or equivalent.

• Strong experience with performance and load testing using at least one of:

  • JMeter
  • k6
  • Gatling
• Ability to interpret performance results and identify whether bottlenecks originate from the application, network, platform, or test setup.
• Strong understanding of API test design, regression testing, and test data management.
• Experience working with complex enterprise or B2B integration environments.

API and Integration Testing

• Strong experience designing tests from OpenAPI 3.0 specifications.
• Ability to identify functional, boundary, negative, and error scenarios from API contracts.
• Strong understanding of parity testing between legacy and migrated API implementations.
• Experience comparing API behavior across response codes, schemas, and business-relevant response content.
• Ability to design and execute multi-step end-to-end integration scenarios.
• Understanding of when to use live dependencies versus mocks or test doubles.
• Experience creating efficient regression suites for complex API landscapes.

Performance Testing

• Proven experience designing and delivering performance tests that include baseline measurement, load ramp-up, sustained load, and result analysis.
• Ability to model realistic production traffic and usage patterns.
• Strong understanding of latency, throughput, concurrency, and timeout constraints.
• Ability to distinguish genuine platform or application performance issues from test-harness or infrastructure effects.
• Experience validating APIs against defined non-functional performance requirements.

Test Automation and CI/CD

• Experience integrating automated API tests into GitLab CI/CD or similar delivery pipelines.
• Ability to configure automated quality gates so that failed tests can block deployment stages.
• Experience producing clear automated test reports suitable for technical review and UAT evidence.
• Understanding of how automated testing fits within deployment and release workflows.

UAT and Quality Ownership

• Experience taking ownership of UAT test execution and final QA sign-off.
• Ability to produce structured test evidence covering expected results, actual results, and pass/fail outcomes.
• Strong judgement when determining whether an implementation is ready to progress to production.
• Ability to communicate defects, test risks, and release readiness clearly to technical and project stakeholders.

Nice to Have

• Experience testing TMF Open API implementations.
• Familiarity with MEF Sonata standards.
• Experience testing Quickwork journeys or similar iPaaS integrations.
• Experience with contract testing tools such as Pact or equivalent.
• German language skills.

Leadership and Working Style

• Able to operate independently as the QA authority within a cross-functional integration team.
• Strong analytical and troubleshooting skills.
• Comfortable challenging implementation quality and withholding sign-off when evidence is insufficient.
• Able to collaborate closely with developers, architects, DevOps, and project leadership.
• Structured and methodical approach to test coverage, evidence, and release readiness.
• Strong communication skills and the ability to explain quality risks clearly to both technical and non-technical stakeholders.