Question

I have the following C code that uses sqlite3:

if(SQLITE_OK == sqlite3_initialize()) {
    self->db_open_result = sqlite3_open(self->db_uri, &(self->db));
} else {
    self->db_open_result = SQLITE_ERROR;
}

Obviously I have a pretty high confidence that the code is correct and will behave as expected. However, I am measuring code coverage of my unit tests using gcov/lcov and I’m curious about how I might get my coverage number to 100% in this case. Under normal circumstances sqlite3_initialize() is never going to fail, so the else clause will never execute.

Is there a way to cause this to fail that isn’t totally disruptive?

Answer 1

You want your unit-tests to test your code. But you also want to know that all of your test code has been properly exercised. One way to do that is to use “mocking”, i.e. you replace your actual libraries (such as SQLite) with fake, or “mock” libraries and then run your programs against these fake libraries.

Whether this library replacement is done at compile time or runtime is really incidental, but in C it’s easier to do it at compile time. You can do this mocking by hand, or you can use a tool such as Cmock.

In the faked library, you then provoke various errors and failures. Notably, the faked library doesn’t even have to do anything or even keep track of much or any state, you can often get quite far by returning “OK” or “FAIL”.