Improve coverage computation

tests/test-mworker.c

@@ -20,8 +20,9 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
-#include <stdio.h>
-#include <assert.h>
+#include "m-core.h"
+#include "coverage.h"
+
 #include "m-worker.h"
 
 /* Compute Fibonacci number using thread systems. */