Description of the method

Decision testing belongs to the family of logical coverages, as it's concerned with the values of logical predicates in deciding instructions. The other name for the technique comes from there: predicate coverage. A decision is simply a logical statement that can take the value of true or false.

Decision result – an output of a decision, determining the branch to follow

Examples of deciding instructions:

• if conditional instruction: if (decision) then …;

• while instruction condition: while (decision) do …;

• do-while instruction condition: do … while (decision);

• switch-case instruction;

• for loop instruction condition: for (initialization; decision; incrementation) do condition …;

Decision testing requires that every instruction in the program takes the logical value of true and false at least once each. For example if the following instruction exists in a program:

if (x > 0 and y == 0) then …

then the (x > 0 ∧ y = 0) condition must be true at least once and must be false at least once. The result can be forced to be true by for example assuming that: x = 1 and y = 0, and to be false by having: x = 1 and y = 1.

In the case of the `switch-case` instruction, it is required that the variable in the `switch` statement takes all possible values specified in the `case` fragments. The construction

switch(x)
  case y1: ... break;
  case y2: ... break;
  ...
  case yn: ... break;
```

can be expressed as a multiple `if-then-else` instruction:

if (x == y1) then
  ...
else if (x == y2) then
  ...
else if (x == yn) then
  ...
endif

Accepting one of the logical conditions in a `switch-case` instruction as true automatically implies that the remaining conditions are logically false.

**Decision**  – a point in a program where the control flow has two or more alternative paths; a node in the control flow graph from which two or more branches emerge.

Just like in the case of branch coverage, in the decision coverage criterion we add a formal condition of instruction coverage, so that the criterion subsumes instruction coverage for programs composed of single basic blocks, not involving any branching

Task 3

section 9.3.1, part 3. Translate the below text and delete the picture

Task 4

section 9.3.1, part 4. Translate the below text and delete the picture