Static Vs. Dynamic Testing

In the ISTQB book one of the first things mentioned in Chapter 3 is dynamic testing and static testing.


Dynamic testing involves executing a software with a set of given input values and then checking the outputs values and comparing them to the expected results.  Static testing involves using either a set of tools or manually examining software work products such as user guides, test cases, and scenarios but not actually executing them, reviews are actually an example of static testing at work.  Basically dynamic testing actually tests the software code while static testing looks through the documents.


Static and dynamic testing techniques are complimentary due to the fact that dynamic testing works on areas static testing does not and visa versa.  When they are used together they can greatly improve the quality of testing and help find a lot more defects.  Static testing methods are good for finding deviations from standards, missing requirements, design defects, non-maintainable code and inconsistent interface specifications.  Dynamic testing is good for finding defects in the code itself, as well as the quality of the software.  Static testing is good in the early stages of testing and in reviews while dynamic testing is good for the main executions.


Since a lot of the info in the ISTQB book is about the dynamic aspects of testing I'll go more in depth with static testing According to ISTQB the use of static testing, e.g. reviews, on software work products has various advantages:
Since static testing can start early in the life cycle, early feedback on quality issues can be established, e.g. an early validation of user requirements and not just late in the life cycle during acceptance testing.
By detecting defects at an early stage, rework costs are most often relatively low and thus a relatively cheap improvement of the quality of software products can be achieved.
Since rework effort is substantially reduced, development productivity figures are likely to increase.
The evaluation by a team has the additional advantage that there is an exchange of information between the participants.
Static tests contribute to an increased awareness of quality issues.