Additional documentation for test scripts

Added documentation in comments in test scripts, added example site.sh,
moved evaluation of site.sh later in lib.sh to allow site.sh to override
more lib.sh variables.

test/lib.sh

@@ -1,5 +1,9 @@
 #!/usr/bin/env bash
 # Define test functions.
+# See numerous configuration variables later on in this file that you can set
+# in the environment or the site.sh file. The definitions in the site.sh file 
+# override 
+#
 # Create working dir as variable "dir"
 # The functions are somewhat wildgrown, a little too many:
 # - expectfn
@@ -17,8 +21,11 @@
 # Testfile (not including path)
 : ${testfile:=$(basename $0)}
 
-# Add test to this list that you dont want run
-# Typically add them in your site file
+# SKIPLIST lists the filenames of the test files that you do *not* want to run.
+# The format is a whitespace separated list of filenames. Specify the SKIPLIST
+# either in the shell environment or in the site.sh file. Any SKIPLIST specified
+# in site.sh overrides a SKIPLIST specified in the environment. If not specified
+# in either the environment or the site.sh, then the default SKIPLIST is empty.
 : ${SKIPLIST:=""}
 
 # Some tests (openconfig/yang_models) just test for the cli to return a version
@@ -34,21 +41,6 @@ if [ -f ./config.sh ]; then
     fi
 fi
 
-# Site file, an example of this file in README.md
-if [ -f ./site.sh ]; then
-    . ./site.sh
-    if [ $? -ne 0 ]; then
-	return -1 # skip
-    fi
-    # test skiplist.
-    for f in $SKIPLIST; do
-	if [ "$testfile" = "$f" ]; then
-	    echo "...skipped (see site.sh)"
-	    return -1 # skip
-	fi
-    done
-fi
-
 # Test number from start
 : ${testnr:=0}
 
@@ -122,7 +114,6 @@ fi
 
 # Standard IETF RFC yang files. 
 : ${IETFRFC=../yang/standard}
-#: ${IETFRFC=$YANGMODELS/standard/ietf/RFC}
 
 # Backend user
 BUSER=clicon
@@ -141,6 +132,23 @@ BUSER=clicon
 
 : ${clixon_backend:=clixon_backend}
 
+# Source the site-specific definitions for test script variables, if site.sh
+# exists. The variables defined in site.sh override any variables of the same
+# names in the environment in the current execution.
+if [ -f ./site.sh ]; then
+    . ./site.sh
+    if [ $? -ne 0 ]; then
+	return -1 # skip
+    fi
+    # test skiplist.
+    for f in $SKIPLIST; do
+	if [ "$testfile" = "$f" ]; then
+	    echo "...skipped (see site.sh)"
+	    return -1 # skip
+	fi
+    done
+fi
+
 dir=/var/tmp/$0
 if [ ! -d $dir ]; then
     mkdir $dir