add errors tests

test/errors.js

@@ -0,0 +1,17 @@
+var chai = require('chai');
+var assert = chai.assert;
+var errors = require('../lib/web3/errors');
+
+describe('lib/web3/method', function () {
+    describe('getCall', function () {
+
+        for(var key in errors) {
+            it('should return and error', function () {
+        
+                assert.instanceOf(errors[key](), Error);
+            });
+        }
+
+    });
+});
+