Statement Coverage Example

This code snippet contains five statements. To achieve 100% statement coverage, you need at least one test with positive x values, one test with negative x values, and one test with x values of zero.

if (x > 0)
  printf( "x is positive" );
else if (x < 0)
  printf( "x is negative" );
else
  printf( "x is 0" );

Condition Coverage Example

In this expression:

y = x<=5 || x!=7;

there are two conditions:

x<=5
x!=7

To achieve 100% condition coverage, your test cases need to demonstrate a true and false outcome for both conditions. For example, a test case where x is equal to 4 demonstrates a true case for both conditions, and a case where x is equal to 7 demonstrates a false case for both conditions.

Boolean Assignment Statements

Code coverage analyzes assignment statements that contain Boolean values and reports them as a condition. Model coverage only analyzes logical expressions in assignment statements, meaning only expressions that contain a logical operator such as the logical AND (&&) or the logical OR (||). This difference can result in a discrepancy between model and code coverage results and can sometimes result in unsatisfiable condition outcomes in the code coverage analysis.

For example, consider the following statement:

bool A = true;

During code coverage analysis, Simulink Coverage analyzes this statement for condition coverage. The statement is true at every time step, so the result is that you get 50% condition coverage on this statement because the false case cannot occur. Model coverage does not analyze this statement, so it also creates a discrepancy between model and code coverage results.

Decision Coverage Example

This code snippet contains three decisions:

y = x<=5 && x!=7;				// decision #1

if( x > 0 )					// decision #2
  printf( "decision #2 is true" );
else if( x < 0 && y )				// decision #3
  printf( "decision #3 is true" ); 
else
  printf( "decisions #2 and #3 are false" );

To achieve 100% decision coverage, your test cases must demonstrate a true and false outcome for each decision.

Modified Condition/Decision Coverage Example

For this decision:

X || ( Y && Z )

the following set of test cases delivers 100% MCDC coverage.

In order to demonstrate that the conditions Y and Z can independently affect the decision outcome, the condition X must be false for those test cases. If the condition X is true, then the decision is already known to be true. Therefore, the conditions Y and Z would not affect the decision outcome.

Limitations

For code coverage, MCDC is limited to expressions that contain 1000 or less logical combinations. If an expression contains more than 1000 logical combinations, Simulink Coverage analyzes MCDC until reaching the 1000 logical combinations limit, then displays a warning that MCDC analysis is incomplete.

Coverage Example

For this code snippet, the cyclomatic complexity is 3:

void evalNum(int x)
{
  if (x > 0)                          // decision #1
    printf( "x is positive" );
  else if (x < 0)                     // decision #2
    printf( "x is negative" );
  else
    printf( "x is 0" );
}

The code contains one function that has two decision points. Each decision point has two outcomes. Using the preceding formula, N is 2, o₁ is 2, and o₂ is 2. Code coverage uses the formula with these decisions and outcomes and adds 1 for the function. The cyclomatic complexity for this code snippet is: