diff --git a/test/test.helpers.js b/test/test.helpers.js
index ec17c31..7c60bf5 100644
--- a/test/test.helpers.js
+++ b/test/test.helpers.js
@@ -1,11 +1,17 @@
-var libpath = process.env['PROTOTYPER_COV'] ? '../lib-cov' : '../lib';
+var libpath = process.env.PROTOTYPER_COV ? '../lib-cov' : '../lib';
 
 var helpers = require(libpath + '/helpers.js');
-var expect = require('chai').expect;
+var markers = require(libpath + '/markers.js');
+var chai = require('chai');
+chai.Assertion.includeStack = true; // defaults to false
+var expect = chai.expect;
 var when = require('when');
 
 
 describe('Helpers', function () {
+	"use strict";
+	var config = { debug: false };
+	var markersInstance = markers(config);
 	var marker_prefix = '<!--\\s*@@';
 	var marker_postfix = '\\s*-->';
 	var helper = helpers({
@@ -13,19 +19,130 @@ describe('Helpers', function () {
 		postfix: marker_postfix
 	});
 
-	describe('replace', function (done) {
-		it('', function () {
-			var promise = helper.replace(null, null, null, true);
-			expect(promise).to.be.an('object');
-			when(promise).then(
-				function onSuccess(result) {
-					expect(result).to.be.an('object');
-					expect(result).to.be.empty();
-					done();
-				}, function onFailure(err) {
-					done(err);
+	describe('replace', function () {
+
+		describe('non matching text input', function () {
+			function testText(text) {
+				return function testText(done) {
+					function onSuccess(result) {
+						try {
+							expect(result).to.be.an('object');
+							expect(result).to.be.empty;
+						} catch (e) {
+							return done(e);
+						}
+						done();
+					}
+
+					function onFailure(err) {
+						done(err);
+					}
+
+					var promise = helper.replace(text, null, null, true);
+					expect(when.isPromise(promise)).to.be.ok;
+					promise.then(onSuccess, onFailure);
+				};
+			}
+
+			var i, values = [ null, undefined, '', 'hello', {}, []];
+			for (i=0; i < values.length; i += 1) {
+				it('should ignore non text input ' + values[i], testText(values[i]));
+			}
+		});
+		describe('check getReplacement', function () {
+
+			it('should call getReplacement fail on error', function (done) {
+				var marker = '<!-- @@null -->';
+				var text = 'hello' + marker + 'world';
+
+				function getReplacement(result, callback) {
+					expect(result).to.be.equal(marker);
+					expect(callback).to.be.a('function');
+					callback('replacementError');
 				}
-			);
-		})
+
+				var promise = helper.replace(text, null, getReplacement, true);
+				expect(when.isPromise(promise)).to.be.ok;
+				promise.then(
+					function onSuccess(result) {
+						done(new Error(JSON.stringify(result)));
+					}, function onFailure(err) {
+						expect(err).to.equal('replacementError');
+						done();
+					}
+				);
+			});
+
+			it('should call getReplacement', function (done) {
+				var marker = '<!-- @@null -->';
+				var text = 'Hello' + marker + 'World' + marker + '!!';
+
+				function getReplacement(result, callback) {
+					console.log('result', result);
+					expect(result).to.be.equal(marker);
+					expect(callback).to.be.a('function');
+					callback(null, {});
+				}
+				var once = true;
+				var promise = helper.replace(text, null, getReplacement, once);
+				expect(when.isPromise(promise)).to.be.ok;
+				promise.then(
+					function onSuccess(result) {
+						try{
+							expect(result).to.be.instanceof(Array);
+							expect(result).to.have.length(1); // due to once == true
+							expect(result[0]).to.be.ok;
+							expect(result[0].replacement).to.not.be.ok;
+							expect(result[0]).to.have.property('regExp');
+							expect(result[0].regExp.source).to.equal('<!--\\s*@@null\\s*-->');
+						}catch(e){
+							// work around 'when eating exceptions'
+							return done(e);
+						}
+						done();
+					}, function onFailure(err) {
+						done(new Error(JSON.stringify(err)));
+					}
+				);
+			});
+
+			it('should call getReplacement', function (done) {
+				var marker = '<!-- @@null -->';
+				var text = 'Hello' + marker + 'World' + marker + '!!';
+
+				function getReplacement(result, callback) {
+					console.log('result', result);
+					expect(result).to.be.equal(marker);
+					expect(callback).to.be.a('function');
+					callback(null, { value: '#'});
+
+				}
+				var once = false;
+				var promise = helper.replace(text, null, getReplacement, once);
+				expect(when.isPromise(promise)).to.be.ok;
+				promise.then(
+					function onSuccess(result) {
+						try{
+							expect(result).to.be.instanceof(Array);
+							expect(result).to.have.length(2); // due to 'once' being false
+							for(var i=0; i<result.length; i += 1) {
+								expect(result[i]).to.be.ok;
+								expect(result[i]).to.have.property('replacement','#');
+								expect(result[i]).to.have.property('regExp');
+								expect(result[i].regExp.source).to.equal('<!--\\s*@@null\\s*-->');
+							}
+						}catch(e){
+							// work around 'when eating exceptions'
+							return done(e);
+						}
+						done();
+					}, function onFailure(err) {
+						done(new Error(JSON.stringify(err)));
+					}
+				);
+			});
+
+
+		});
 	});
 });