The report is devoted to design of functional testing based on application functions segregation, which is the base of paradigm “One function = one test”; In this paradigm function is put against business case, it provides test granularity and rapid localization of defects. Assuming the application is a Finite-State Machine, the function is a set of only state and only its output transitions. This approach allows to define functional testing coverage and to limit the number of tests. The report supposes demonstration of functionality testing framework based on free software with open source Apache Jmeter. Target Audience of the report is test-designers and test-analysts worked on functional testing of applications.