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Given-When-Then (GWT) is a semi-structured way to write down test cases. They can either be tested manually or automated as browser tests with tools like Selenium and Cucumber. [1] [2] It derives its name from the three clauses used, which start with the words given, when and then. [3]
The routine in the following example written in Eiffel takes as an argument an integer which must be a valid value for an hour of the day, i. e., 0 through 23, inclusively. The precondition follows the keyword require. It specifies that the argument must be greater than or equal to zero and less than or equal to 23.
A condition is shown to affect a decision's outcome independently by varying just that condition while holding fixed all other possible conditions. The condition/decision criterion does not guarantee the coverage of all conditions in the module because in many test cases, some conditions of a decision are masked by the other conditions. Using ...
For example, a precondition—an assertion placed at the beginning of a section of code—determines the set of states under which the programmer expects the code to execute. A postcondition—placed at the end—describes the expected state at the end of execution. For example: x > 0 { x++ } x > 1.
All preconditions that are not modified by the expression can be carried over to the postcondition. In the first example, assigning y := x + 1 {\displaystyle y:=x+1} does not change the fact that x + 1 = 43 {\displaystyle x+1=43} , so both statements may appear in the postcondition.
In such cases, DbC makes the supplier's job easier. Design by contract also defines criteria for correctness for a software module: If the class invariant AND precondition are true before a supplier is called by a client, then the invariant AND the postcondition will be true after the service has been completed.
In this example, two test cases are sufficient to achieve a complete branch coverage, while four are necessary for complete path coverage. The cyclomatic complexity of the program is 3 (as the strongly connected graph for the program contains 9 edges, 7 nodes, and 1 connected component) ( 9 − 7 + 1 ).
A test case graph illustrates all the necessary independent paths (test cases) to cover all isolated conditions. Conditions are represented by nodes, and condition values (situations) by edges. An edge addresses all program situations. Each situation is connected to one preceding and successive condition.