added tests

index.js

 var localRegex = new RegExp(regStr);
 var globalRegex = new RegExp(regStr, "g");
 
+function expectType(type, val) {
+	if (typeof val !== type)
+		throw new TypeError("Expected "+type+", got "+typeof val);
+}
+
+function expectInstance(obj, val) {
+	if (!(val instanceof obj)) {
+		var regex = /function (.+)\(/;
+		var expectedName = obj.toString().match(regex)[1];
+
+		try {
+			var realName = val.constructor.toString().match(regex)[1];
+		} catch (err) {
+			var realName = "undefined";
+		}
+
+		throw new TypeError("Expected "+expectedName+", got "+realName);
+	}
+}
+
 function hasMultipleStatements(str) {
 	return (str.indexOf(";") !== -1)
 }
 Func.prototype = Function.prototype;
 
 function Templish(str, vals) {
+	expectType("string", str);
+	expectInstance(Array, vals);
+
 	str = str.replace(/\s+/g, " ").replace(/}}/g, "}}\n");
 	this.string = str;
 	this.vals = vals;
 }
 
 Templish.prototype.exec = function(vals, cb) {
+	expectInstance(Object, vals);
+	expectType("function", cb);
+
 	var str = this.string;
 
 	//Prepare generic arguments

package.json

 {
   "name": "templish",
-  "version": "0.0.2",
+  "version": "0.0.3",
   "description": "HTML templating library for JS",
   "main": "index.js",
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "mocha test"
   },
   "author": "Martin Dørum Nygaard",
   "license": "MIT",

test/test.js

+var assert = require("assert");
+var Templish = require("../index.js");
+
+describe("templish", function() {
+	it("does basic substitution", function(done) {
+		var t = new Templish("{{conf.foo}}", ["conf"]);
+		t.exec({conf: {foo: "bar"}}, function(err, res) {
+			assert.equal(res, "bar");
+			done(err);
+		});
+	});
+
+	it("does basic async substitution", function(done) {
+		var t = new Templish("{{cb(null, 'hi')}}", []);
+		t.exec({}, function(err, res) {
+			assert.equal(res, "hi");
+			done(err);
+		});
+	});
+
+	it("does a mix of async and sync substitution", function(done) {
+		var t = new Templish("{{'a'}} {{cb(null, 'b')}} {{'c'}} {{cb(null, 'd')}}", []);
+		t.exec({}, function(err, res) {
+			assert.equal(res, "a b c d");
+			done(err);
+		});
+	});
+
+	it("doesn't break when the result of a substitution looks like a template", function(done) {
+		var t = new Templish("foo: {{foo}}, again: {{foo}}", ["foo"]);
+		t.exec({foo: "{{foo}}"}, function(err, res) {
+			assert.equal(res, "foo: {{foo}}, again: {{foo}}");
+			done(err);
+		});
+	});
+});