diff --git a/index.js b/index.js
index 949d146f..16ad407d 100755
--- a/index.js
+++ b/index.js
@@ -72,7 +72,7 @@ util.inherits(Sharp, stream.Duplex);
 Sharp.prototype._write = function(chunk, encoding, callback) {
   /*jslint unused: false */
   if (this.options.streamIn) {
-    if (typeof chunk === 'object' || chunk instanceof Buffer) {
+    if (typeof chunk === 'object' && chunk instanceof Buffer) {
       if (typeof this.options.bufferIn === 'undefined') {
         // Create new Buffer
         this.options.bufferIn = new Buffer(chunk.length);
@@ -98,13 +98,10 @@ module.exports.gravity = {'center': 0, 'centre': 0, 'north': 1, 'east': 2, 'sout
 
 Sharp.prototype.crop = function(gravity) {
   this.options.canvas = 'c';
-  if (typeof gravity !== 'undefined') {
-    // Is this a supported gravity?
-    if (!Number.isNaN(gravity) && gravity >= 0 && gravity <= 4) {
-      this.options.gravity = gravity;
-    } else {
-      throw new Error('Unsupported crop gravity ' + gravity);
-    }
+  if (typeof gravity === 'number' && !Number.isNaN(gravity) && gravity >= 0 && gravity <= 4) {
+    this.options.gravity = gravity;
+  } else {
+    throw new Error('Unsupported crop gravity ' + gravity);
   }
   return this;
 };
@@ -264,7 +261,7 @@ Sharp.prototype.resize = function(width, height) {
   if (!width) {
     this.options.width = -1;
   } else {
-    if (!Number.isNaN(width)) {
+    if (typeof width === 'number' && !Number.isNaN(width)) {
       this.options.width = width;
     } else {
       throw new Error('Invalid width ' + width);
@@ -273,7 +270,7 @@ Sharp.prototype.resize = function(width, height) {
   if (!height) {
     this.options.height = -1;
   } else {
-    if (!Number.isNaN(height)) {
+    if (typeof height === 'number' && !Number.isNaN(height)) {
       this.options.height = height;
     } else {
       throw new Error('Invalid height ' + height);
@@ -458,10 +455,10 @@ Sharp.prototype.metadata = function(callback) {
   Get and set cache memory and item limits
 */
 module.exports.cache = function(memory, items) {
-  if (Number.isNaN(memory)) {
+  if (typeof memory !== 'number' || Number.isNaN(memory)) {
     memory = null;
   }
-  if (Number.isNaN(items)) {
+  if (typeof items !== 'number' || Number.isNaN(items)) {
     items = null;
   }
   return sharp.cache(memory, items);
@@ -471,7 +468,7 @@ module.exports.cache = function(memory, items) {
   Get and set size of thread pool
 */
 module.exports.concurrency = function(concurrency) {
-  if (Number.isNaN(concurrency)) {
+  if (typeof concurrency !== 'number' || Number.isNaN(concurrency)) {
     concurrency = null;
   }
   return sharp.concurrency(concurrency);
diff --git a/test/unit/alpha.js b/test/unit/alpha.js
index b33814d9..1b6f9a87 100755
--- a/test/unit/alpha.js
+++ b/test/unit/alpha.js
@@ -30,11 +30,24 @@ describe('Alpha transparency', function() {
       .toFile(fixtures.path('output.flatten-hex-orange.jpg'), done);
   });
 
+  it('Do not flatten', function(done) {
+    sharp(fixtures.inputPngWithTransparency)
+      .flatten(false)
+      .toBuffer(function(err, data) {
+        if (err) throw err;
+        sharp(data).metadata(function(err, metadata) {
+          if (err) throw err;
+          assert.strictEqual('png', metadata.format);
+          assert.strictEqual(4, metadata.channels);
+          done();
+        });
+      });
+  });
+
   it('Ignored for JPEG', function(done) {
     sharp(fixtures.inputJpg)
       .background('#ff0000')
       .flatten()
-      .resize(500, 400)
       .toBuffer(function(err, data) {
         if (err) throw err;
         sharp(data).metadata(function(err, metadata) {
diff --git a/test/unit/colourspace.js b/test/unit/colourspace.js
index 2feb5d72..be3b67ff 100755
--- a/test/unit/colourspace.js
+++ b/test/unit/colourspace.js
@@ -22,6 +22,13 @@ describe('Colour space conversion', function() {
       .toFile(fixtures.path('output.greyscale-gamma-2.2.jpg'), done);
   });
 
+  it('Not to greyscale', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(320, 240)
+      .greyscale(false)
+      .toFile(fixtures.path('output.greyscale-not.jpg'), done);
+  });
+
   it('From 1-bit TIFF to sRGB WebP [slow]', function(done) {
     sharp(fixtures.inputTiff)
       .webp()
diff --git a/test/unit/crop.js b/test/unit/crop.js
index f02efe1b..c9e8ff11 100755
--- a/test/unit/crop.js
+++ b/test/unit/crop.js
@@ -79,4 +79,15 @@ describe('Crop gravities', function() {
       });
   });
 
+  it('Invalid', function(done) {
+    var isValid = true;
+    try {
+      sharp(fixtures.inputJpg).crop(5);
+    } catch (err) {
+      isValid = false;
+    }
+    assert.strictEqual(false, isValid);
+    done();
+  });
+
 });
diff --git a/test/unit/gamma.js b/test/unit/gamma.js
index da57b207..9542a13a 100755
--- a/test/unit/gamma.js
+++ b/test/unit/gamma.js
@@ -1,5 +1,7 @@
 'use strict';
 
+var assert = require('assert');
+
 var sharp = require('../../index');
 var fixtures = require('../fixtures');
 
@@ -10,12 +12,14 @@ describe('Gamma correction', function() {
       .resize(129, 111)
       .toFile(fixtures.path('output.gamma-0.0.jpg'), done);
   });
+
   it('value of 2.2 (default)', function(done) {
     sharp(fixtures.inputJpgWithGammaHoliness)
       .resize(129, 111)
       .gamma()
       .toFile(fixtures.path('output.gamma-2.2.jpg'), done);
   });
+
   it('value of 3.0', function(done) {
     sharp(fixtures.inputJpgWithGammaHoliness)
       .resize(129, 111)
@@ -23,4 +27,15 @@ describe('Gamma correction', function() {
       .toFile(fixtures.path('output.gamma-3.0.jpg'), done);
   });
 
+  it('invalid value', function(done) {
+    var isValid = true;
+    try {
+      sharp(fixtures.inputJpgWithGammaHoliness).gamma(4);
+    } catch (err) {
+      isValid = false;
+    }
+    assert.strictEqual(false, isValid);
+    done();
+  });
+
 });
diff --git a/test/unit/io.js b/test/unit/io.js
index 3ede1b15..cc733d4e 100755
--- a/test/unit/io.js
+++ b/test/unit/io.js
@@ -67,6 +67,18 @@ describe('Input/output', function() {
     readable.pipe(pipeline);
   });
 
+  it('Read from Stream and write to Buffer via Promise', function(done) {
+    var readable = fs.createReadStream(fixtures.inputJpg);
+    var pipeline = sharp().resize(1, 1);
+    pipeline.toBuffer().then(function(data) {
+      assert.strictEqual(true, data.length > 0);
+      done();
+    }).catch(function(err) {
+      throw err;
+    });
+    readable.pipe(pipeline);
+  });
+
   it('Read from Stream and write to Stream', function(done) {
     var readable = fs.createReadStream(fixtures.inputJpg);
     var writable = fs.createWriteStream(fixtures.outputJpg);
@@ -114,6 +126,34 @@ describe('Input/output', function() {
     readableButNotAnImage.pipe(writable);
   });
 
+  it('Sequential read', function(done) {
+    sharp(fixtures.inputJpg)
+      .sequentialRead()
+      .resize(320, 240)
+      .toBuffer(function(err, data, info) {
+        if (err) throw err;
+        assert.strictEqual(true, data.length > 0);
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(240, info.height);
+        done();
+      });
+  });
+
+  it('Not sequential read', function(done) {
+    sharp(fixtures.inputJpg)
+      .sequentialRead(false)
+      .resize(320, 240)
+      .toBuffer(function(err, data, info) {
+        if (err) throw err;
+        assert.strictEqual(true, data.length > 0);
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(240, info.height);
+        done();
+      });
+  });
+
   it('Fail when output File is input File', function(done) {
     sharp(fixtures.inputJpg).toFile(fixtures.inputJpg, function(err) {
       assert(!!err);
@@ -121,6 +161,33 @@ describe('Input/output', function() {
     });
   });
 
+  it('Fail when output File is input File via Promise', function(done) {
+    sharp(fixtures.inputJpg).toFile(fixtures.inputJpg).then(function(data) {
+      assert(false);
+      done();
+    }).catch(function(err) {
+      assert(!!err);
+      done();
+    });
+  });
+
+  it('Fail when output File is empty', function(done) {
+    sharp(fixtures.inputJpg).toFile('', function(err) {
+      assert(!!err);
+      done();
+    });
+  });
+
+  it('Fail when output File is empty via Promise', function(done) {
+    sharp(fixtures.inputJpg).toFile('').then(function(data) {
+      assert(false);
+      done();
+    }).catch(function(err) {
+      assert(!!err);
+      done();
+    });
+  });
+
   it('Fail when input is empty Buffer', function(done) {
     var fail = false;
     try {
@@ -161,6 +228,42 @@ describe('Input/output', function() {
     });
   });
 
+  it('Invalid quality', function(done) {
+    var isValid = true;
+    try {
+      sharp(fixtures.inputJpg).quality(-1);
+    } catch (err) {
+      isValid = false;
+    }
+    assert.strictEqual(false, isValid);
+    done();
+  });
+
+  it('Progressive image', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(320, 240)
+      .png()
+      .progressive(false)
+      .toBuffer(function(err, nonProgressive, info) {
+        if (err) throw err;
+        assert.strictEqual(true, nonProgressive.length > 0);
+        assert.strictEqual('png', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(240, info.height);
+        sharp(nonProgressive)
+          .progressive()
+          .toBuffer(function(err, progressive, info) {
+            if (err) throw err;
+            assert.strictEqual(true, progressive.length > 0);
+            assert.strictEqual(true, progressive.length > nonProgressive.length);
+            assert.strictEqual('png', info.format);
+            assert.strictEqual(320, info.width);
+            assert.strictEqual(240, info.height);
+            done();
+          });
+      });
+  });
+
   describe('Output filename without extension uses input format', function() {
 
     it('JPEG', function(done) {
diff --git a/test/unit/metadata.js b/test/unit/metadata.js
index 9e70c17e..36ad3bbd 100755
--- a/test/unit/metadata.js
+++ b/test/unit/metadata.js
@@ -99,7 +99,7 @@ describe('Image metadata', function() {
     });
   });
 
-  it('Promise', function(done) {
+  it('File in, Promise out', function(done) {
     sharp(fixtures.inputJpg).metadata().then(function(metadata) {
       assert.strictEqual('jpeg', metadata.format);
       assert.strictEqual(2725, metadata.width);
@@ -111,6 +111,23 @@ describe('Image metadata', function() {
     });
   });
 
+  it('Stream in, Promise out', function(done) {
+    var readable = fs.createReadStream(fixtures.inputJpg);
+    var pipeline = sharp();
+    pipeline.metadata().then(function(metadata) {
+      assert.strictEqual('jpeg', metadata.format);
+      assert.strictEqual(2725, metadata.width);
+      assert.strictEqual(2225, metadata.height);
+      assert.strictEqual('srgb', metadata.space);
+      assert.strictEqual(3, metadata.channels);
+      assert.strictEqual(false, metadata.hasAlpha);
+      done();
+    }).catch(function(err) {
+      throw err;
+    });
+    readable.pipe(pipeline);
+  });
+
   it('Stream', function(done) {
     var readable = fs.createReadStream(fixtures.inputJpg);
     var pipeline = sharp().metadata(function(err, metadata) {
diff --git a/test/unit/resize.js b/test/unit/resize.js
index 3e4048ae..9fdfd7f9 100755
--- a/test/unit/resize.js
+++ b/test/unit/resize.js
@@ -62,6 +62,28 @@ describe('Resize dimensions', function() {
     });
   });
 
+  it('Invalid width', function(done) {
+    var isValid = true;
+    try {
+      sharp(fixtures.inputJpg).resize('spoons', 240);
+    } catch (err) {
+      isValid = false;
+    }
+    assert.strictEqual(false, isValid);
+    done();
+  });
+
+  it('Invalid height', function(done) {
+    var isValid = true;
+    try {
+      sharp(fixtures.inputJpg).resize(320, 'spoons');
+    } catch (err) {
+      isValid = false;
+    }
+    assert.strictEqual(false, isValid);
+    done();
+  });
+
   it('TIFF embed known to cause rounding errors', function(done) {
     sharp(fixtures.inputTiff).resize(240, 320).embed().jpeg().toBuffer(function(err, data, info) {
       if (err) throw err;
@@ -117,26 +139,46 @@ describe('Resize dimensions', function() {
     });
   });
 
-  it('Do not enlarge if input width is already less than output width', function(done) {
-    sharp(fixtures.inputJpg).resize(2800).withoutEnlargement().toBuffer(function(err, data, info) {
-      if (err) throw err;
-      assert.strictEqual(true, data.length > 0);
-      assert.strictEqual('jpeg', info.format);
-      assert.strictEqual(2725, info.width);
-      assert.strictEqual(2225, info.height);
-      done();
-    });
+  it('Do not enlarge when input width is already less than output width', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(2800)
+      .withoutEnlargement()
+      .toBuffer(function(err, data, info) {
+        if (err) throw err;
+        assert.strictEqual(true, data.length > 0);
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(2725, info.width);
+        assert.strictEqual(2225, info.height);
+        done();
+      });
   });
 
-  it('Do not enlarge if input height is already less than output height', function(done) {
-    sharp(fixtures.inputJpg).resize(null, 2300).withoutEnlargement().toBuffer(function(err, data, info) {
-      if (err) throw err;
-      assert.strictEqual(true, data.length > 0);
-      assert.strictEqual('jpeg', info.format);
-      assert.strictEqual(2725, info.width);
-      assert.strictEqual(2225, info.height);
-      done();
-    });
+  it('Do not enlarge when input height is already less than output height', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(null, 2300)
+      .withoutEnlargement()
+      .toBuffer(function(err, data, info) {
+        if (err) throw err;
+        assert.strictEqual(true, data.length > 0);
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(2725, info.width);
+        assert.strictEqual(2225, info.height);
+        done();
+      });
+  });
+
+  it('Do enlarge when input width is less than output width', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(2800)
+      .withoutEnlargement(false)
+      .toBuffer(function(err, data, info) {
+        if (err) throw err;
+        assert.strictEqual(true, data.length > 0);
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(2800, info.width);
+        assert.strictEqual(2286, info.height);
+        done();
+      });
   });
 
 });
diff --git a/test/unit/sharpen.js b/test/unit/sharpen.js
new file mode 100755
index 00000000..1d09fd04
--- /dev/null
+++ b/test/unit/sharpen.js
@@ -0,0 +1,34 @@
+'use strict';
+
+var assert = require('assert');
+
+var sharp = require('../../index');
+var fixtures = require('../fixtures');
+
+describe('Sharpen', function() {
+
+  it('sharpen image is larger than non-sharpen', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(320, 240)
+      .sharpen(false)
+      .toBuffer(function(err, notSharpened, info) {
+        if (err) throw err;
+        assert.strictEqual(true, notSharpened.length > 0);
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(240, info.height);
+        sharp(notSharpened)
+          .sharpen()
+          .toBuffer(function(err, sharpened, info) {
+            if (err) throw err;
+            assert.strictEqual(true, sharpened.length > 0);
+            assert.strictEqual(true, sharpened.length > notSharpened.length);
+            assert.strictEqual('jpeg', info.format);
+            assert.strictEqual(320, info.width);
+            assert.strictEqual(240, info.height);
+            done();
+          });
+      });
+  });
+
+});
diff --git a/test/unit/util.js b/test/unit/util.js
index 6f917135..e1e7291d 100755
--- a/test/unit/util.js
+++ b/test/unit/util.js
@@ -9,10 +9,20 @@ describe('Utilities', function() {
 
   describe('Cache', function() {
     it('Can be disabled', function() {
-      sharp.cache(0);
+      var cache = sharp.cache(0, 0);
+      assert.strictEqual(0, cache.memory);
+      assert.strictEqual(0, cache.items);
     });
     it('Can be set to a maximum of 50MB and 500 items', function() {
+      var cache = sharp.cache(50, 500);
+      assert.strictEqual(50, cache.memory);
+      assert.strictEqual(500, cache.items);
+    });
+    it('Ignores invalid values', function() {
       sharp.cache(50, 500);
+      var cache = sharp.cache('spoons');
+      assert.strictEqual(50, cache.memory);
+      assert.strictEqual(500, cache.items);
     });
   });
 
@@ -25,6 +35,11 @@ describe('Utilities', function() {
       sharp.concurrency(0);
       assert.strictEqual(defaultConcurrency, sharp.concurrency());
     });
+    it('Ignores invalid values', function() {
+      sharp.concurrency(0);
+      sharp.concurrency('spoons');
+      assert.strictEqual(defaultConcurrency, sharp.concurrency());
+    });
   });
 
   describe('Counters', function() {