  Use case scenarios are created during the analysis phase to specify software
system requirements and can also be used for creating system level test cases.
Using use cases to get system tests has several benefits including test design
at early stages of software development life cycle that reduces over all
development cost of the system. Current approaches for system testing using use
cases involve functional details and does not include guards as passing
criteria i.e. use of class diagram that seem to be difficult at very initial
level which lead the need of specification based testing without involving
functional details. In this paper, we proposed a technique for system testing
directly derived from the specification without involving functional details.
We utilize initial and post conditions applied as guards at each level of the
use cases that enables us generation of formalized test cases and makes it
possible to generate test cases for each flow of the system. We used use case
scenarios to generate system level test cases, whereas system sequence diagram
is being used to bridge the gap between the test objective and test cases,
derived from the specification of the system. Since, a state chart derived from
the combination of sequence diagrams can model the entire behavior of the
system.Generated test cases can be employed and executed to state chart in
order to capture behavior of the system with the state change.All these steps
enable us to systematically refine the specification to achieve the goals of
system testing at early development stages.
