Add in document on rule testing.

docs/rule-testing.md

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+# Rule Testing
+
+It is often easier to test out DLO rules on your site without having to actually add them to the website code first.   This can be done by using a Developer Console and entering in Javascript snippets that represent rules.  
+
+If you are testing on a page that already has DLO loaded, you'll want to make sure to set DLO into preview mode, and then you can register individual rules.  This can be done as such:
+
+```   
+    window['_dlo_observer'].config.previewMode = true;
+    window['_dlo_observer'].registerRule( { <someRule> } );
+```
+
+If you are testing on a page that does not have DLO loaded, you can load DLO manually.  In this case, you can either setup rules into a window expando that starts with `_dlo_rules`, for example `window[_dlo_rules_testing] = [ <somerules> ]` or you can load DLO manually and then manually register rules as above.   To manually load DLO you can do the following:
+
+```
+ window['_dlo_appender'] = 'console';
+ window['_dlo_beforeDestination'] = [{ name: 'convert', enumerate: true, index: -1 }, { name: 'suffix' }, { name: 'insert', value: 'dlo', position: -1 }];
+ window['_dlo_previewMode'] = true;
+ window['_dlo_readOnLoad'] = true;
+ window['_dlo_validateRules'] = true;
+ window['_dlo_logLevel'] = 1;
+  (function (d, script) {
+   script = d.createElement('script');
+   script.type = 'text/javascript';
+   script.async = true;
+   script.src = 'https://edge.fullstory.com/datalayer/v1/latest.js';
+   d.getElementsByTagName('head')[0].appendChild(script);
+ }(document));
+```
+
+Here is an example snippet that combines both approaches to detect whether DLO is already loaded on the page and take the appropriate action.  
+
+```
+// add your rules here
+window['_dlo_rules_testing'] = [{
+  "id": "fs-gtg-event",
+  "source": "dataLayer",
+  "operators": [
+    { "name": "query", "select": "$[(0,1,2)]" },
+    { "name": "query", "select": "$[?(0=event)]" },
+    { "name": "flatten" },
+    { "name": "rename", "properties": { "0": "gtgCommand", "1": "gtgAction" } },
+    { "name": "query", "select": "$[?(gtgCommand!^gtm)]" },
+    { "name": "query", "select": "$[?(gtgCommand!=optimize.domChange)]" },
+    { "name": "query", "select": "$[?(ecommerce=undefined)]" },
+    { "name": "insert", "select": "gtgAction" }
+  ],
+  "destination": "FS.event"
+}];
+
+// Look for DLO on page and take approprate action to load the rules 
+if (window['_dlo_observer']) {
+ window['_dlo_observer'].config.previewMode = true;
+ window['_dlo_rules_testing'].forEach(function (rule) {
+   window['_dlo_observer'].registerRule(rule);
+ });
+} else {
+ window['_dlo_appender'] = 'console';
+ window['_dlo_beforeDestination'] = [{ name: 'convert', enumerate: true, index: -1 }, { name: 'suffix' }, { name: 'insert', value: 'dlo', position: -1 }];
+ window['_dlo_previewMode'] = true;
+ window['_dlo_readOnLoad'] = true;
+ window['_dlo_validateRules'] = true;
+ window['_dlo_logLevel'] = 1;
+  (function (d, script) {
+   script = d.createElement('script');
+   script.type = 'text/javascript';
+   script.async = true;
+   script.src = 'https://edge.fullstory.com/datalayer/v1/latest.js';
+   d.getElementsByTagName('head')[0].appendChild(script);
+ }(document));
+}
+
+```