Question

I’ve been starting to use CppUnit library. And everything worked fine, but now, I get stuck with asserting iterators using CPPUNIT_ASSERT_EQUAL. So there is my code:

void TestingClass::test_adjacent_find()
{
    // Set up
    int a [5] = {1,2,3,3,5};
    int b [5] = {1,2,3,4,5};
    int c [1] = {1};

    std::list<int> lst;
    lst.push_back(1);
    lst.push_back(1);
    lst.push_back(5);

    // Check
    CPPUNIT_ASSERT_EQUAL(a+2, my_adjacent_find(a , a+5, pred_eq<int>));
    CPPUNIT_ASSERT_EQUAL(b+5, my_adjacent_find(b, b+5, pred_eq<int>));
    CPPUNIT_ASSERT_EQUAL(c+1, my_adjacent_find(c, c+1, pred_eq<int>));
    CPPUNIT_ASSERT_EQUAL(lst.begin(), lst.end()); // problem is here
}

When I’m running this test I’m getting the error below.

/opt/local/include/cppunit/TestAssert.h:49:13: 
Invalid operands to binary expression 
('OStringStream' (aka 'basic_ostringstream<char>') 
and 'const std::_List_iterator<int>')

If I comment the line with iterators, then it compiles without any problems. So what am I doing wrong? And how should I assert equality of two iterators? By the way, I use xcode 4.4.

Answer 1

See CPPUNIT_ASSERT_EQUAL macro documentation in TestAssert.h:

#define CPPUNIT_ASSERT_EQUAL(expected,actual)

Requirement for expected and actual parameters:

• They are exactly of the same type
• They are serializable into a std::strstream using operator <<
• They can be compared using operator ==.

The last two requirements (serialization and comparison) can be removed by specializing the CppUnit::assertion_traits.

So the root cause of your problem is that std::list::iterator could not be serialized to std::strstream. You need to write your own CppUnit::assertion_traits specialization for it as documentation describes or just avoid CPPUNIT_ASSERT_EQUAL and use CPPUNIT_ASSERT:

CPPUNIT_ASSERT(lst.begin() == lst.end());