Cucumber
Behaviour-driven development tool running acceptance tests written in Gherkin
Doit
Scripting tool for testing web applications that use forms
GraphWalker
Open source model-based testing tool
Hexawise
Combinatorial test design tool
CucumberStudio
Collaboration and test management platform for BDD (formerly Hiptest)
HOL-TestGen
Specification-based test case generator built on Isabelle/HOL