adds arm testing of same files

test/mains/README.md

@@ -1,5 +1,18 @@
-# Method testing
+# Mains testing
 
-Test Whole methods by their output. Using the main method (implicitly)
+Test methods by their output and exit codes (return, since it is the main). 
 
-Through Interpreter
+There are only two tests here, one for interpreter, one for arm.
+Both run the same tests. The actual ruby code that is run is in the source dir.
+Test methods are generated, one for each source file.
+
+File names follow [name,stdout,exitcode] joined by _ pattern. Stdout may be left blank,
+but exit code must be supplied.
+
+Obviously the arm tests need an arm platform. This may be defined by ARM_HOST,
+eg for simulated ARM_HOST=localhost
+
+Also port and user may be specified with ARM_PORT and ARM_USER , they default to
+2222 and pi if left blank.
+SSH keys must be set up so no passwords are required (and the users private key may
+  not be password protected)