2017-07-28: added an example for actually testing a procedure

added an example for actually testing a procedure

diff --git a/examples/doctests-test.scm b/examples/doctests-test.scm
--- a/examples/doctests-test.scm
+++ b/examples/doctests-test.scm
@@ -6,6 +6,12 @@ exec guile -L $(dirname $(dirname $(real
 
 (import (examples doctests))
 
+(define (foo)
+    "(test \"foo\"
+        (test-equal \"bar\" (foo)))
+    "
+    "bar")
+
 (define %this-module (current-module))
 (define (main args)
        " Testing doctests
diff --git a/examples/doctests-test.w b/examples/doctests-test.w
--- a/examples/doctests-test.w
+++ b/examples/doctests-test.w
@@ -8,6 +8,12 @@ define-module : examples doctests-test
 
 import : examples doctests
 
+define : foo
+    . "(test \"foo\"
+        (test-equal \"bar\" (foo)))
+    "
+    . "bar"
+
 define %this-module : current-module
 define : main args
        . " Testing doctests