Add simple test to verify pure-ness of plain validate() call

test/pure.js

@@ -0,0 +1,40 @@
+'use strict';
+
+/*jsl predef:define*/
+/*jsl predef:it*/
+
+var Validator = require('../lib/validator');
+var should = require('chai').should();
+
+describe('API', function () {
+  describe('arguments are pure', function () {
+    // Pure meaning they aren't modified by the function call
+    beforeEach(function () {
+      this.validator = new Validator();
+    });
+
+    it('"dependencies" constraint', function () {
+      var data = {
+        "foo": [1,2,3],
+        "bar": 2
+      };
+      var schema = {
+        "dependencies": {
+          "bar": {
+            "properties": {
+              "foo": {
+                "type": "array",
+                "items": {"type":"integer"}
+              },
+              "bar": {"type": "integer"}
+            },
+            "required": ["foo", "bar"]
+          }
+        }
+      };
+      Object.freeze(data.foo);
+      Object.freeze(data);
+      this.validator.validate(data, schema);
+    });
+  });
+});