ACTS
Combinatorial (t-way) test generation tool from NIST
ibello
Test automation framework for web applications and back-end systems
Doc Sheets
Requirements, test case and lifecycle management tool (formerly CASE Spec)
Keploy
Open source tool that turns application traffic into tests and mocks
Schemathesis
Property-based API testing from OpenAPI and GraphQL schemas
Reqnroll
Cucumber-style BDD framework for .NET, successor of SpecFlow