Atlantis TDD (2) Unit Testing

Before I get to write any more implementation, it’s time to write some tests for my interfaces. I like to use CuTest for this, because it’s small, pure C, doesn’t try to be fancy, and there’s only a single file to link to. And now I’m writing tests for every function in the interface and its edge cases:

static void test_get_regions(CuTest * tc)
{
  struct region * results[4];
  void * cur;
  icursor * icur;
  int i, n = 0;

  svc.reset();

  for (i=0;i!=3;++i) {
    svc.regions->create(0, i);
  }
  cur = svc.get_regions(&icur);
  CuAssertPtrNotNull(tc, cur);
  CuAssertPtrNotNull(tc, icur);
  CuAssertIntEquals(tc, 3, icur->get(cur, 4, (void**)results));
  for (i=0;i!=3;++i) {
    int x, y;
    svc.regions->get_xy(results[i], &x, &y);
    CuAssertIntEquals(tc, 0, x);
    n |= (1<<y);
  }
  CuAssertIntEquals(tc, 7, n);

  CuAssertIntEquals(tc, 3, icur->advance(&cur, 4));
  CuAssertIntEquals(tc, 0, icur->advance(&cur, 4));
  if (icur->destroy) icur->destroy(cur);
}

This function tests the cursor returned by the get_regions function that I talked about in my previous post. As tests go, it’s pretty big: after first creating 3 regions, it asserts that the cursor will return those regions, will only return three even if asked for four, and that it’s able to advance until it reaches the end. Notice how, once again, the code is entirely written in terms of the new interface. I tend to write “struct region” instead of “region” for the type here, to remind myself that I don’t have access to the members of my objects, and apart from knowing it’s a struct, I really don’t know anything about it.

Now, I can’t run this test yet, because to don that, I would need an actual implementation of the interface to test. Since I haven’t broken out the Atlantis source yet, I’m going to write my own implementation of the data structures that does the bare minimum, and hook it up to the interfaces. You can see the result of that in the mock directory of my github project. This reference implementation will also allow me to test my game logic later without having to link against Atlantis or Eressea.

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