Created Testing (asciidoc)

Testing.asciidoc

@@ -0,0 +1,19 @@
+### General testing tips
+
+Define a "testing" conditional symbol at compile time: nim --define:testing main.nim
+
+``` Nim
+when defined(testing):
+  # testing-related code
+else:
+  # production code
+```
+
+### Unit testing
+
+http://nim-lang.org/unittest.html[unittest]
+
+### Functional and integration testing
+
+### Code coverage
+