Add very simple test for precompile

Related to #392

tests/precompile.js

@@ -0,0 +1,22 @@
+(function() {
+    'use strict';
+
+    var expect, precompile, precompileString;
+
+    if(typeof require !== 'undefined') {
+        expect = require('expect.js');
+        precompile = require('../src/precompile').precompile;
+        precompileString = require('../src/precompile').precompileString;
+    }
+    else {
+        expect = window.expect;
+        precompile = nunjucks.precompile;
+        precompileString = nunjucks.precompileString
+    }
+
+    describe('precompile', function() {
+        it('should return a string', function() {
+            expect(precompileString("{{ test }}", { name: "test.html" })).to.be.an('string');
+        });
+    });
+})();