FIX: test suite for connetion - changed types to class

src/connection_m.fun

@@ -7,13 +7,13 @@
 test_suite connection_m
 
 ! Global variables declaration
-type(mock_neuron_t), target :: n1
-type(mock_neuron_t), target :: n2
+class(neuron_t), target :: n1
+class(neuron_t), target :: n2
 
-type(mock_neuron_t), pointer :: n1_p
-type(mock_neuron_t), pointer :: n2_p
+class(neuron_t), pointer :: n1_p
+class(neuron_t), pointer :: n2_p
 
-type(mock_neuron_t), pointer :: dummy_p
+class(neuron_t), pointer :: dummy_p
 
 type(connection_t), pointer :: con