Code Coverage Criteria

When we write tests for a codebase, it is common to wonder how good is the test-suite. One way to measure it is through code coverage. That is: how much how the code base is covered by the tests? Most of the time, this notion is not precise. Most tools measuring code coverage can give you a percentage of the coverage, without a clear definition.

Yet there exists some precise definitions for various ways of measuring code coverage. They are called code coverage criteria.

Function Coverage

The easiest one is called function coverage (FC). It measure the percentage of the functions of your programs that are called by the test-suite. For instance, if your whole code base has only two functions, and in your test-suite, only one of them gets execution, then it means you have a function coverage of 50%.

Statement Coverage

This criteria (SC) measure the percentage of instructions of your program that are executed.

Decision Coverage

This criteria (DC) measure the percentage of decisions covered for you test-suite. For instance, if you have some code looking like the following:

void f(int x) {
  if (x) {
    // A
  } else {
    // B
  }
}

When the conditional is reached, there are two possible decisions. If x is true, then, we execute A. If x is false, then, we execute B.

Condition Coverage

This criteria (CC) ... TODO

TODO

All the others (MC/DC)

TODO: explain that there is a correspondence with the CFG (covering nodes versus covering edges and such)

References

TODO