diff --git a/index.js b/index.js
index 82f47b02..f13eb08c 100644
--- a/index.js
+++ b/index.js
@@ -363,7 +363,8 @@
             var that = this;
             decree(defs.args.toBuffer)(arguments, function(type, params, callback) {
                 if (type === 'jpg' || type === 'jpeg') {
-                    params.quality = params.quality || defs.defaults.DEF_JPEG_QUALITY;
+                    if (params.quality != 0)
+                        params.quality = params.quality || defs.defaults.DEF_JPEG_QUALITY;
                     if (params.quality != parseInt(params.quality) || params.quality < 0 || params.quality > 100)
                         throw Error('Invalid JPEG quality');
                     return encoder.jpeg(
@@ -637,15 +638,14 @@
         var that = this;
         decree(defs.args.toBuffer)(arguments, function(type, params, callback) {
             if (type === 'jpg' || type === 'jpeg') {
-                params.quality = params.quality || defs.defaults.DEF_JPEG_QUALITY;
+                if (params.quality != 0)
+                    params.quality = params.quality || defs.defaults.DEF_JPEG_QUALITY;
                 if (params.quality != parseInt(params.quality) || params.quality < 0 || params.quality > 100)
                     throw Error('Invalid JPEG quality');
             } else if (type === 'png') {
                 params.compression = params.compression || defs.defaults.PNG_DEF_COMPRESSION;
-                if (params.compression === 'none') params.compression = 0;
-                else if (params.compression === 'fast') params.compression = 1;
-                else if (params.compression === 'high') params.compression = 2;
-                else throw Error('Invalid PNG compression');
+                if (['none', 'fast', 'high'].indexOf(params.compression) === -1)
+                    throw Error('Invalid PNG compression');
                 params.interlaced = params.interlaced || defs.defaults.PNG_DEF_INTERLACED;
                 if (typeof params.interlaced !== 'boolean') throw Error('PNG \'interlaced\' must be boolean');
             } else throw Error('Unknown type \'' + type + '\'');
diff --git a/tests/02.operations/01.writeFile.js b/tests/02.operations/01.writeFile.js
index 8475c70c..8541f10a 100644
--- a/tests/02.operations/01.writeFile.js
+++ b/tests/02.operations/01.writeFile.js
@@ -111,6 +111,7 @@ describe('lwip.writeFile', function() {
             });
 
             describe('params specified - high compression, not interlaced', function() {
+                this.timeout(4000); // 4 seconds. high compression can take more time
                 it('should succeed', function(done) {
                     image.writeFile(outpathPng, {
                         compression: 'high',
@@ -120,6 +121,7 @@ describe('lwip.writeFile', function() {
             });
 
             describe('params specified - high compression, interlaced', function() {
+                this.timeout(4000); // 4 seconds. high compression can take more time
                 it('should succeed', function(done) {
                     image.writeFile(outpathPng, {
                         compression: 'high',
diff --git a/tests/03.batch/index.js b/tests/03.batch/index.js
index c6b28bd6..0b6fa0e3 100644
--- a/tests/03.batch/index.js
+++ b/tests/03.batch/index.js
@@ -2,48 +2,226 @@ var join = require('path').join,
     assert = require('assert'),
     mkdirp = require('mkdirp'),
     lwip = require('../../'),
+    utils = require('../utils'),
     imgs = require('../imgs');
 
-var tmpDir = join(__dirname, '../results'),
-    basename = 'batch',
-    current;
-
 describe('image.batch', function() {
 
-    before(function(done) {
-        mkdirp(tmpDir, done);
-    });
+    var ops, batch;
 
-    var batch;
     beforeEach(function(done) {
         lwip.open(imgs.jpg.rgb, function(err, img) {
+            if (err) return done(err);
             batch = img.batch();
-            done(err);
+            ops = utils.generateRandomBatch(batch, 3);
+            done();
         });
     });
 
-    beforeEach(function() {
-        current = [basename];
-    });
+    describe('toBuffer', function() {
 
-    afterEach(function(done) {
-        batch.writeFile(join(tmpDir, current.join('_') + '.jpg'), 'jpeg', {
-            quality: 100
-        }, done);
-    });
+        describe('jpeg', function() {
+
+            describe('quality 0', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer('jpg', {
+                        quality: 0
+                    }, function(err, buffer) {
+                        done(err);
+                    });
+                });
+            });
+
+            describe('quality 100', function() {
+                it('should succeed', function(done) {
+                    batch.toBuffer('jpg', {
+                        quality: 100
+                    }, function(err, buffer) {
+                        done(err);
+                    });
+                });
+            });
 
-    describe('rotate(45,yellow)->crop(200,200)->blur(5)', function() {
-        it('should succeed', function() {
-            current.push('rotate45yellow', 'crop200X200', 'blur5');
-            batch.rotate(45, 'yellow').crop(200, 200).blur(5);
         });
+
+        describe('png', function() {
+
+            describe('non interlaced', function() {
+
+                describe('no compression', function() {
+                    it('should succeed', function(done) {
+                        batch.toBuffer('png', {
+                            interlaced: false,
+                            compression: 'none',
+                        }, function(err, buffer) {
+                            done(err);
+                        });
+                    });
+                });
+
+                describe('fast compression', function() {
+                    it('should succeed', function(done) {
+                        batch.toBuffer('png', {
+                            interlaced: false,
+                            compression: 'fast',
+                        }, function(err, buffer) {
+                            done(err);
+                        });
+                    });
+                });
+
+                describe('high compression', function() {
+                    this.timeout(4000); // 4 seconds. high compression can take more time
+                    it('should succeed', function(done) {
+                        batch.toBuffer('png', {
+                            interlaced: false,
+                            compression: 'high',
+                        }, function(err, buffer) {
+                            done(err);
+                        });
+                    });
+                });
+
+            });
+
+            describe('interlaced', function() {
+
+                describe('no compression', function() {
+                    it('should succeed', function(done) {
+                        batch.toBuffer('png', {
+                            interlaced: true,
+                            compression: 'none',
+                        }, function(err, buffer) {
+                            done(err);
+                        });
+                    });
+                });
+
+                describe('fast compression', function() {
+                    it('should succeed', function(done) {
+                        batch.toBuffer('png', {
+                            interlaced: true,
+                            compression: 'fast',
+                        }, function(err, buffer) {
+                            done(err);
+                        });
+                    });
+                });
+
+                describe('high compression', function() {
+                    this.timeout(4000); // 4 seconds. high compression can take more time
+                    it('should succeed', function(done) {
+                        batch.toBuffer('png', {
+                            interlaced: true,
+                            compression: 'high',
+                        }, function(err, buffer) {
+                            done(err);
+                        });
+                    });
+                });
+
+            });
+
+        });
+
     });
 
-    describe('rotate(-20,green)->scale(2)->crop(500,500)', function() {
-        it('should succeed', function() {
-            current.push('rotate-20green', 'scale2', 'crop500X500');
-            batch.rotate(-20, 'green').scale(2).crop(500, 500);
+    describe('writeFile', function() {
+
+        var tmpDir = join(__dirname, '../results');
+
+        before(function(done) {
+            mkdirp(tmpDir, done);
+        });
+
+        describe('jpeg', function() {
+
+            describe('quality 0', function() {
+                it('should succeed', function(done) {
+                    batch.writeFile(join(tmpDir, 'btch-q0-' + ops.join('#') + '.jpg'), 'jpg', {
+                        quality: 0
+                    }, done);
+                });
+            });
+
+            describe('quality 100', function() {
+                it('should succeed', function(done) {
+                    batch.writeFile(join(tmpDir, 'btch-q100-' + ops.join('#') + '.jpg'), 'jpg', {
+                        quality: 100
+                    }, done);
+                });
+            });
+
+        });
+
+        describe('png', function() {
+
+            describe('non interlaced', function() {
+
+                describe('no compression', function() {
+                    it('should succeed', function(done) {
+                        batch.writeFile(join(tmpDir, 'btch--noint#nocomp--' + ops.join('#') + '.png'), 'png', {
+                            interlaced: false,
+                            compression: 'none',
+                        }, done);
+                    });
+                });
+
+                describe('fast compression', function() {
+                    it('should succeed', function(done) {
+                        batch.writeFile(join(tmpDir, 'btch--noint#fstcomp--' + ops.join('#') + '.png'), 'png', {
+                            interlaced: false,
+                            compression: 'fast',
+                        }, done);
+                    });
+                });
+
+                describe('high compression', function() {
+                    this.timeout(4000); // 4 seconds. high compression can take more time
+                    it('should succeed', function(done) {
+                        batch.writeFile(join(tmpDir, 'btch-noint#hicomp-' + ops.join('#') + '.png'), 'png', {
+                            interlaced: false,
+                            compression: 'high',
+                        }, done);
+                    });
+                });
+
+            });
+
+            describe('interlaced', function() {
+
+                describe('no compression', function() {
+                    it('should succeed', function(done) {
+                        batch.writeFile(join(tmpDir, 'btch-intr#nocomp-' + ops.join('#') + '.png'), 'png', {
+                            interlaced: true,
+                            compression: 'none',
+                        }, done);
+                    });
+                });
+
+                describe('fast compression', function() {
+                    it('should succeed', function(done) {
+                        batch.writeFile(join(tmpDir, 'btch-intr#fstcomp-' + ops.join('#') + '.png'), 'png', {
+                            interlaced: true,
+                            compression: 'fast',
+                        }, done);
+                    });
+                });
+
+                describe('high compression', function() {
+                    this.timeout(4000); // 4 seconds. high compression can take more time
+                    it('should succeed', function(done) {
+                        batch.writeFile(join(tmpDir, 'btch-intr#hicomp-' + ops.join('#') + '.png'), 'png', {
+                            interlaced: true,
+                            compression: 'high',
+                        }, done);
+                    });
+                });
+
+            });
+
         });
+
     });
 
 });
diff --git a/tests/04.stress/index.js b/tests/04.stress/index.js
index d1b73459..39ddda1d 100644
--- a/tests/04.stress/index.js
+++ b/tests/04.stress/index.js
@@ -1,8 +1,10 @@
 var join = require('path').join,
+    fs = require('fs'),
     assert = require('assert'),
     async = require('async'),
     mkdirp = require('mkdirp'),
     lwip = require('../../'),
+    utils = require('../utils'),
     imgs = require('../imgs');
 
 var tmpDir = join(__dirname, '../results'),
@@ -64,50 +66,14 @@ describe('stress tests', function() {
                 lwip.open(imgs.jpg.rgb, 'jpeg', function(err, image) {
                     if (err) return done(err);
                     var batch = image.batch();
-                    for (var i = 0; i < 10; i++) {
-                        var r = Math.floor(Math.random() * 12);
-                        switch (r) {
-                            case 0:
-                                batch = batch.blur(5);
-                                break;
-                            case 1:
-                                batch = batch.rotate(45);
-                                break;
-                            case 2:
-                                batch = batch.resize(600, 200);
-                                break;
-                            case 3:
-                                batch = batch.crop(100, 150);
-                                break;
-                            case 4:
-                                batch = batch.scale(1.1, 0.66);
-                                break;
-                            case 5:
-                                batch = batch.mirror('xy');
-                                break;
-                            case 6:
-                                batch = batch.border(10);
-                                break;
-                            case 7:
-                                batch = batch.sharpen(300);
-                                break;
-                            case 8:
-                                batch = batch.saturate(1.2);
-                                break;
-                            case 9:
-                                batch = batch.lighten(0.5);
-                                break;
-                            case 10:
-                                batch = batch.darken(0.5);
-                                break;
-                            case 11:
-                                batch = batch.hue(-50);
-                                break;
-                        }
-                    }
-                    batch.writeFile(outpathJpeg, 'jpeg', {
+                    var ops = utils.generateRandomBatch(batch, 10);
+                    batch.writeFile(join(tmpDir, 'stress-rnd-' + i + '.jpg'), 'jpeg', {
                         quality: 50
-                    }, done);
+                    }, function(err) {
+                        if (err) return done(err);
+                        var data = ops.join('\n');
+                        fs.writeFile(join(tmpDir, 'stress-rnd-' + i + '.txt'), data, done);
+                    });
                 });
             }, done);
         });
diff --git a/tests/utils.js b/tests/utils.js
new file mode 100644
index 00000000..fc5a2a04
--- /dev/null
+++ b/tests/utils.js
@@ -0,0 +1,77 @@
+module.exports = {
+    generateRandomBatch: generateRandomBatch
+};
+
+function generateRandomBatch(batch, n) {
+    var ops = [];
+    for (var i = 0; i < n; i++) {
+        var r = Math.floor(Math.random() * 12);
+        switch (r) {
+            case 0:
+                var sd = Math.floor(Math.random() * 20);
+                batch = batch.blur(sd);
+                ops.push('blr' + sd);
+                break;
+            case 1:
+                var a = Math.floor(Math.random() * 360);
+                batch = batch.rotate(a);
+                ops.push('rtt' + a);
+                break;
+            case 2:
+                var w = Math.floor(Math.random() * 1000) + 1;
+                var h = Math.floor(Math.random() * 1000) + 1;
+                batch = batch.resize(w, h);
+                ops.push('rsz' + w + 'X' + h);
+                break;
+            case 3:
+                var w = Math.floor(Math.random() * 1000);
+                var h = Math.floor(Math.random() * 1000);
+                batch = batch.crop(w, h);
+                ops.push('crp' + w + 'X' + h);
+                break;
+            case 4:
+                var wr = Math.random() * 3 + 0.1;
+                var hr = Math.random() * 3 + 0.1;
+                batch = batch.scale(wr, hr);
+                ops.push('scl' + wr.toFixed(2) + 'X' + hr.toFixed(2));
+                break;
+            case 5:
+                var i = Math.floor(Math.random() * 3);
+                var axes = ['x', 'y', 'xy'][i];
+                batch = batch.mirror(axes);
+                ops.push('mrr' + axes);
+                break;
+            case 6:
+                var b = Math.floor(Math.random() * 30);
+                batch = batch.border(b);
+                ops.push('brdr' + b);
+                break;
+            case 7:
+                var amp = Math.floor(Math.random() * 300);
+                batch = batch.sharpen(amp);
+                ops.push('shrp' + amp);
+                break;
+            case 8:
+                var d = Math.random() * 2;
+                batch = batch.saturate(d);
+                ops.push('sat' + d.toFixed(2));
+                break;
+            case 9:
+                var d = Math.random() * 2;
+                batch = batch.lighten(d);
+                ops.push('lit' + d.toFixed(2));
+                break;
+            case 10:
+                var d = Math.random() * 0.5;
+                batch = batch.darken(d);
+                ops.push('drk' + d.toFixed(2));
+                break;
+            case 11:
+                var s = Math.floor(Math.random() * 360);
+                batch = batch.hue(s);
+                ops.push('hue' + s);
+                break;
+        }
+    }
+    return ops;
+}