Is it O.K. to use global data for multiple tests in the TDD cycle within the Google Test framework?

Question

I have just started using Gtest, and I am writing tests that look like this:

TEST(testFamily, specificTest) {
     initData data; 
     ASSERT_TRUE(boolean_algorithm(data)); 
}

The problem is that my testing code gets unnecesarily bloated because I have a lot of tests that can use the same data, so the line:

 initData data; 

shouldn't be repeated for each test. I know that tests should be independent of each other and in that aspect, using something like a constant global

const initData data; 

brings questions like "Are you sure your tests won't modify the global test data?". Should i keep initializing the same test configuration for each test? Sometimes the initialized test data requires much more code than one line....

Answer 1

It is ok, but I would create that object in the testing class, rather then in the global scope (like explained in Test Fixtures: Using the Same Data Configuration for Multiple Tests).

For example, like this :

initData CreateData() 
{
    initData d;
    // set values
    return d;
}

class testFamily : public testing::Test
{
public:
    testFamily() :
            data( CreateData()  )
    {
    }
    ~testFamily()
    {
    }

    initData data;
};

TEST_F( testFamily, specificTest )
{
    ASSERT_TRUE(boolean_algorithm(data)); 
}

Now, the data structure is calculated (or set) only in one place (CreateData() function).