combines and dries the two program tests

test/small_program_test.rb

@@ -3,7 +3,8 @@ require_relative 'helper'
 # test the generation of a whole program
 # not many asserts, but assume all is  well (ho ho)
 # linking and running does not produce seqmentation fault, ie it works
-# moving on to calling external functions to get some output
+# should really thiink about more asserts (but currently no way to execute as still running on mac )
+#    (have to fix the int being used in code generation as ruby int is only 31 bits, and that wont do)
 
 class TestSmallProg < MiniTest::Test
   # need a code generator, for arm 
@@ -19,13 +20,34 @@ class TestSmallProg < MiniTest::Test
       subs r0, r0, 1          #2
       bne loop_start          #3
     	mov r7, 1               #4
-    	swi 0                   #5  5 instruction x 4 == 20
+    	swi 0                   #5  5 instructions
     }
+    write( 5 , "small" )
+  end
+  
+  def test_extern
+    @generator.instance_eval {
+      mov r0 , 50             #1
+      push lr                 #2
+      bl extern(:putchar)     #3
+    	pop pc                  #4 
+      mov r7, 1               #5
+    	swi 0                   #6  6 instructions
+    }
+    #this actually seems to get an extern symbol out there and linker is ok (but doesnt run, hmm)
+    @generator.relocations.each { |reloc|
+      #puts "reloc #{reloc.inspect}"
+      writer.add_reloc_symbol reloc.label.name.to_s
+    }
+    write( 6 , "extern")
+  end
 
+  #helper to write the file
+  def write len ,name
     writer = Asm::ObjectWriter.new(Elf::Constants::TARGET_ARM)
     assembly = @generator.assemble
-    assert_equal 20 , assembly.length 
+    assert_equal len * 4 , assembly.length 
     writer.set_text assembly
-    writer.save('small_test.o')    
+    writer.save('#{name}_test.o')    
   end
 end