Add field test

test/field.test.js

@@ -0,0 +1,18 @@
+var assert = require('assert');
+var tree = require('../lib/carto/tree.js');
+require('../lib/carto/tree/field');
+
+describe('Field', function() {
+    describe('basic functionality', function() {
+        it('should be constructed', function() {
+            var f = new tree.Field("foo");
+            assert.ok(f);
+            assert.equal(f.is, 'field');
+        });
+        it('should produce xml-friendly output', function() {
+            var f = new tree.Field("bar");
+            assert.ok(f);
+            assert.equal(f.toString(), "[bar]");
+        });
+    });
+});