Do you really know the exact performance of your test cases? Do you build your test cases on the basis of methodological concepts? If an error occurs, do you know immediately, which detail of the test case has caused the error? This white paper is for all testers who would answer one or more questions with “No”. After an introduction to the methodological basics of TestCase-Design, we will present you with Linear Expansion. This method allows optimal test cases to be created, i.e. you are able to gain maximum test coverage with a reduced number of test cases.