What is code coverage and how do YOU measure it?

Question

What is code coverage and how do YOU measure it?

I was asked this question regarding our automating testing code coverage. It seems to be that, outside of automated

Answer 1

Complementing a few points to many of the previous answers:

Code coverage means, how well your test set is covering your source code. i.e. to what extent is the source code covered by the set of test cases.

As mentioned in above answers, there are various coverage criteria, like paths, conditions, functions, statements, etc. But additional criteria to be covered are

1. Condition coverage: All boolean expressions to be evaluated for true and false.
2. Decision coverage: Not just boolean expressions to be evaluated for true and false once, but to cover all subsequent if-elseif-else body.
3. Loop Coverage: means, has every possible loop been executed one time, more than once and zero time. Also, if we have assumption on max limit, then, if feasible, test maximum limit times and, one more than maximum limit times.
4. Entry and Exit Coverage: Test for all possible call and its return value.
5. Parameter Value Coverage (PVC). To check if all possible values for a parameter are tested. For example, a string could be any of these commonly: a) null, b) empty, c) whitespace (space, tabs, new line), d) valid string, e) invalid string, f) single-byte string, g) double-byte string. Failure to test each possible parameter value may leave a bug. Testing only one of these could result in 100% code coverage as each line is covered, but as only one of seven options are tested, means, only 14.2% coverage of parameter value.
6. Inheritance Coverage: In case of object oriented source, when returning a derived object referred by base class, coverage to evaluate, if sibling object is returned, should be tested.

Note: Static code analysis will find if there are any unreachable code or hanging code, i.e. code not covered by any other function call. And also other static coverage. Even if static code analysis reports that 100% code is covered, it does not give reports about your testing set if all possible code coverage is tested.