This paper presents the SAGA toolbox. It centers around development of tests, and analysis of test results, on Guarded Assertions (GA) format. Such a test defines when to test, and what to expect in such a state. The SAGA toolbox lets the user describe the test, and at the same time get immediate feedback on the test result based on a trace from the System Under Test (SUT). The feedback is visual using plots of the trace. This enables the test engineer to play around with the data and use an agile development method, since the data is already there. Moreover, the SAGA toolbox also enables the test engineer to change test stimuli plots to study the effect they have on a test. It can later generate computer programs that can feed these test stimuli to the SUT. This enables an interactive feedback loop, where immediate feedback on changes to the test, or to the test stimuli, indicate whether the test is correct and it passed or failed.