Added test for sp_network being set when calling sp_find_network

Author: markjfisher

testing/bdd-testing/features/apple2/fn_network/sp_find_network.feature

@@ -7,6 +7,7 @@ Feature: library test - apple2 sp_find_network
       And I add common apple2-sp files
       And I add file for compiling "features/apple2/fn_network/invokers/test_sp_find_network.s"
       And I create and load apple-single application using crt-file "features/apple2/fn_network/stubs/crt0.s"
+      And I write memory at _sp_network with $FF
      When I execute the procedure at _init for no more than 750 instructions
 
     # offset 5 contains the device name
@@ -22,3 +23,6 @@ Feature: library test - apple2 sp_find_network
      # return from _sp_find_network is 2 for Device number
      And I expect register A equal 2
      And I expect register X equal 0
+
+     # Check _sp_network is altered to correct value
+     And I expect to see _sp_network equal 2