Factors considered to decide test strategy or test approach :

(1) Analytical Approach: This test approach is based on an analysis of some factor, which strongly effects the testing environment, e.g., Requirements might be analyzed in order to design a test approach such that the most important requirements get tested first and test cases for other requirements get designed / executed later. Another exercise commonly performed is Risk Analysis, where tests are designed and prioritized such that the critical risks get eliminated at the earliest possible time. This approach is an example of preventive test approach, since we are analyzing and prioritizing test cases early on, based on an analysis of some factor contributing to the testing environment.

(2) Model-based approach: the tests are designed based on some mathematical or stochastic (statistical) model of the object functionality. As an example, if a model predicts the failure rates of a particular system (or software) under some conditions, and the failure rate of our product is as stipulated by the model under the specified conditions, then our product is assumed to be working fine. This approach pays emphasis on identification and selection of the appropriate model during the early stages of SDLC and is a preventive test approach.

(3) Methodical Approach: This test approach depends heavily upon following a predetermined method to perform testing. The method used can vary widely, ranging from adherence to certain checklists to error guessing and experience-based approaches. Here, tests are designed, executed and implemented in accordance with the selected method. Actual testing effort may get started early on or later during the SDLC when following this testing approach.

(4) Process-or Standard-compliant Approach: As the name suggests, this testing approach recommends designing and creation of test assets based on some externally developed industry standard, e.g., Tests could be designed based on IEEE 829 standards. As an alternative, one of the agile methodologies, such as Extreme Programming (XP), might be adopted. Again, actual testing effort might get started early on or later during the SDLC when this approach is selected.

(5) Dynamic (Heuristic) Approach: This test approach involves performing heuristic testing. Exploratory testing is a good example of the type of testing performed, when this approach is followed. Here, the tests are designed and executed simultaneously, and hence, it is a reactive test approach.

(6) Regression-averse Approach: This approach recommends designing tests such that regression defects get detected at the earliest. This may involve extensive automation of functional regression tests as well as re-use of existing test material.