Test-driven development (TDD) is entering the mainstream of software development. We examined the software development process for the purpose of evaluation of the TDD impact, with respect to software development productivity, in the context of a web based system development. The design of the study is based on Goal-Question-Metric approach, and may be easily replicated in different industrial contexts where the number of subjects involved in the study is limited. The study reveals that TDD may have positive impact on software development productivity. Moreover, TDD is characterized by the higher ratio of active development time (described as typing and producing code) in total development time than test-last development approach.