diff --git a/test/info.test.js b/test/info.test.js
index 2c269d7..1dd19a3 100644
--- a/test/info.test.js
+++ b/test/info.test.js
@@ -2,7 +2,6 @@ process.env.NODE_ENV = 'test';
 
 var fs = require('fs');
 var Step = require('step');
-var assert = require('assert');
 var MBTiles = require('..');
 
 var fixtures = {
@@ -13,7 +12,7 @@ var fixtures = {
 try { fs.unlink(fixtures.empty); } catch (err) {}
 
 
-exports['get metadata'] = function(beforeExit) {
+exports['get metadata'] = function(beforeExit, assert) {
     var completed = false;
 
     new MBTiles(fixtures.plain_1, function(err, mbtiles) {
@@ -48,7 +47,7 @@ exports['get metadata'] = function(beforeExit) {
     });
 };
 
-exports['get/put metadata from empty file'] = function(beforeExit) {
+exports['get/put metadata from empty file'] = function(beforeExit, assert) {
     var completion = {};
 
     new MBTiles(fixtures.empty, function(err, mbtiles) {
diff --git a/test/list.test.js b/test/list.test.js
index 0722a17..3a3523f 100644
--- a/test/list.test.js
+++ b/test/list.test.js
@@ -2,7 +2,6 @@ process.env.NODE_ENV = 'test';
 
 var fs = require('fs');
 var Step = require('step');
-var assert = require('assert');
 var MBTiles = require('..');
 
 var fixtures = {
@@ -12,17 +11,17 @@ var fixtures = {
 try { fs.unlink(fixtures.doesnotexist); } catch (err) {}
 
 
-exports['list'] = function(beforeExit) {
+exports['list'] = function(beforeExit, assert) {
     var completed = false; beforeExit(function() { assert.ok(completed); });
 
     MBTiles.list(fixtures.doesnotexist, function(err, list) {
         assert.ok(err);
-        assert.equal(err.message, 'ENOENT, No such file or directory');
+        assert.ok(err.code.match(/^ENOENT/));
         
         MBTiles.list(fixtures.doesnotexist, function(err, list) {
             completed = true;
             assert.ok(err);
-            assert.equal(err.message, 'ENOENT, No such file or directory');
+            assert.ok(err.code.match(/^ENOENT/));
         });
     });
 };
diff --git a/test/read.test.js b/test/read.test.js
index 3ecddc0..22aa685 100644
--- a/test/read.test.js
+++ b/test/read.test.js
@@ -1,7 +1,6 @@
 process.env.NODE_ENV = 'test';
 
 var fs = require('fs');
-var assert = require('assert');
 var MBTiles = require('..');
 
 
@@ -16,15 +15,17 @@ var fixtures = {
 
 try { fs.unlink(fixtures.non_existent); } catch (err) {}
 
-function yieldsError(status, error, msg) {
+function yieldsError(assert, status, error, msg) {
     return function(err) {
         assert.ok(err);
-        assert.equal(err.message, msg);
+        var re = new RegExp( "^" + msg, "i");
+        assert.ok(err.message.match(re));
         status[error]++;
     };
 }
 
-exports['get tiles'] = function(beforeExit) {
+
+exports['get tiles'] = function(beforeExit, assert) {
     var status = {
         success: 0,
         error: 0
@@ -45,13 +46,13 @@ exports['get tiles'] = function(beforeExit) {
             }
         });
 
-        mbtiles.getTile(0, 1, 0, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(-1, 0, 0, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(0, 0, 1, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(3, 1, -1, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(2, -3, 3, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(18, 2, 262140, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(4, 0, 15, yieldsError(status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(0, 1, 0, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(-1, 0, 0, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(0, 0, 1, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(3, 1, -1, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(2, -3, 3, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(18, 2, 262140, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(4, 0, 15, yieldsError(assert, status, 'error', 'Tile does not exist'));
     });
 
 
@@ -61,7 +62,7 @@ exports['get tiles'] = function(beforeExit) {
     });
 };
 
-exports['get grids'] = function(beforeExit) {
+exports['get grids'] = function(beforeExit, assert) {
     var status = {
         success: 0,
         error: 0
@@ -82,13 +83,13 @@ exports['get grids'] = function(beforeExit) {
             }
         });
 
-        mbtiles.getGrid(0, 1, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(-1, 0, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(0, 0, 1, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(3, 1, -1, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(2, -3, 3, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(18, 2, 262140, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 0, 15, yieldsError(status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(0, 1, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(-1, 0, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(0, 0, 1, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(3, 1, -1, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(2, -3, 3, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(18, 2, 262140, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 0, 15, yieldsError(assert, status, 'error', 'Grid does not exist'));
     });
 
 
@@ -99,7 +100,7 @@ exports['get grids'] = function(beforeExit) {
 };
 
 
-exports['get grids from file without interaction'] = function(beforeExit) {
+exports['get grids from file without interaction'] = function(beforeExit, assert) {
     var status = {
         success: 0,
         error: 0
@@ -107,20 +108,20 @@ exports['get grids from file without interaction'] = function(beforeExit) {
 
     new MBTiles(fixtures.plain_1, function(err, mbtiles) {
         if (err) throw err;
-        mbtiles.getGrid(0, 1, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(-1, 0, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(0, 0, -1, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(3, 1, 8, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(2, -3, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(18, 2, 3, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 0, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 3, 8, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 4, 8, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 5, 8, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 13, 4, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 0, 14, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(3, 0, 7, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(3, 6, 2, yieldsError(status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(0, 1, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(-1, 0, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(0, 0, -1, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(3, 1, 8, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(2, -3, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(18, 2, 3, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 0, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 3, 8, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 4, 8, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 5, 8, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 13, 4, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 0, 14, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(3, 0, 7, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(3, 6, 2, yieldsError(assert, status, 'error', 'Grid does not exist'));
     });
 
     beforeExit(function() {
@@ -129,7 +130,7 @@ exports['get grids from file without interaction'] = function(beforeExit) {
     });
 };
 
-exports['get grids with different schema'] = function(beforeExit) {
+exports['get grids with different schema'] = function(beforeExit, assert) {
     var status = {
         success: 0,
         error: 0
@@ -150,13 +151,13 @@ exports['get grids with different schema'] = function(beforeExit) {
             }
         });
 
-        mbtiles.getGrid(0, 1, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(-1, 0, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(0, 0, 1, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(3, 1, -1, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(2, -3, 3, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(18, 2, 262140, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 0, 15, yieldsError(status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(0, 1, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(-1, 0, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(0, 0, 1, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(3, 1, -1, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(2, -3, 3, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(18, 2, 262140, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 0, 15, yieldsError(assert, status, 'error', 'Grid does not exist'));
     });
 
     beforeExit(function() {
@@ -166,7 +167,7 @@ exports['get grids with different schema'] = function(beforeExit) {
 };
 
 
-exports['get grids from file without interaction'] = function(beforeExit) {
+exports['get grids from file without interaction'] = function(beforeExit, assert) {
     var status = {
         success: 0,
         error: 0
@@ -174,20 +175,20 @@ exports['get grids from file without interaction'] = function(beforeExit) {
 
     new MBTiles(fixtures.plain_1, function(err, mbtiles) {
         if (err) throw err;
-        mbtiles.getGrid(0, 1, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(-1, 0, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(0, 0, -1, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(3, 1, 8, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(2, -3, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(18, 2, 3, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 0, 0, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 3, 8, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 4, 8, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 5, 8, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 13, 4, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(4, 0, 14, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(3, 0, 7, yieldsError(status, 'error', 'Grid does not exist'));
-        mbtiles.getGrid(3, 6, 2, yieldsError(status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(0, 1, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(-1, 0, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(0, 0, -1, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(3, 1, 8, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(2, -3, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(18, 2, 3, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 0, 0, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 3, 8, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 4, 8, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 5, 8, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 13, 4, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(4, 0, 14, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(3, 0, 7, yieldsError(assert, status, 'error', 'Grid does not exist'));
+        mbtiles.getGrid(3, 6, 2, yieldsError(assert, status, 'error', 'Grid does not exist'));
     });
 
     beforeExit(function() {
@@ -196,7 +197,7 @@ exports['get grids from file without interaction'] = function(beforeExit) {
     });
 };
 
-exports['get tiles from non-existent file'] = function(beforeExit) {
+exports['get tiles from non-existent file'] = function(beforeExit, assert) {
     var status = {
         success: 0,
         error: 0
@@ -204,20 +205,20 @@ exports['get tiles from non-existent file'] = function(beforeExit) {
 
     new MBTiles(fixtures.non_existent, function(err, mbtiles) {
         if (err) throw err;
-        mbtiles.getTile(0, 1, 0, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(-1, 0, 0, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(0, 0, -1, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(3, 1, 8, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(2, -3, 0, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(18, 2, 3, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(4, 0, 0, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(4, 3, 8, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(4, 4, 8, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(4, 5, 8, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(4, 13, 4, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(4, 0, 14, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(3, 0, 7, yieldsError(status, 'error', 'Tile does not exist'));
-        mbtiles.getTile(3, 6, 2, yieldsError(status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(0, 1, 0, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(-1, 0, 0, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(0, 0, -1, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(3, 1, 8, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(2, -3, 0, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(18, 2, 3, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(4, 0, 0, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(4, 3, 8, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(4, 4, 8, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(4, 5, 8, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(4, 13, 4, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(4, 0, 14, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(3, 0, 7, yieldsError(assert, status, 'error', 'Tile does not exist'));
+        mbtiles.getTile(3, 6, 2, yieldsError(assert, status, 'error', 'Tile does not exist'));
     });
 
     beforeExit(function() {
@@ -226,7 +227,7 @@ exports['get tiles from non-existent file'] = function(beforeExit) {
     });
 };
 
-exports['get tiles from corrupt file'] = function(beforeExit) {
+exports['get tiles from corrupt file'] = function(beforeExit, assert) {
     var status = {
         success: 0,
         error: 0
@@ -245,3 +246,5 @@ exports['get tiles from corrupt file'] = function(beforeExit) {
         );
     });
 };
+
+
diff --git a/test/reloading.test.js b/test/reloading.test.js
index aaef635..ae46856 100644
--- a/test/reloading.test.js
+++ b/test/reloading.test.js
@@ -1,7 +1,6 @@
 process.env.NODE_ENV = 'test';
 
 var fs = require('fs');
-var assert = require('assert');
 var MBTiles = require('..');
 
 var fixtureDir = __dirname + '/fixtures/output';
@@ -17,7 +16,7 @@ var file = fs.readFileSync(fixtures.source);
 try { fs.unlinkSync(fixtures.destination); } catch(err) {}
 try { fs.mkdirSync(fixtureDir, 0755); } catch(err) {}
 
-exports['test file reloading during copying'] = function(beforeExit) {
+exports['test file reloading during copying'] = function(beforeExit, assert) {
     var completed = false;
     var status = {
         success: 0,
diff --git a/test/write.test.js b/test/write.test.js
index 11b6b3b..c3b0e3d 100644
--- a/test/write.test.js
+++ b/test/write.test.js
@@ -10,7 +10,7 @@ var fixtureDir = __dirname + '/fixtures/output';
 try { fs.unlinkSync(fixtureDir + '/write_1.mbtiles'); } catch(err) {}
 try { fs.mkdirSync(fixtureDir, 0755); } catch(err) {}
 
-exports['test mbtiles file creation'] = function(beforeExit) {
+exports['test mbtiles file creation'] = function(beforeExit, assert) {
     var completed = { written: 0, read: 0 };
     new MBTiles(fixtureDir + '/write_1.mbtiles', function(err, mbtiles) {
         completed.open = true;
diff --git a/test/write_grids.test.js b/test/write_grids.test.js
index 4d30c1e..d22c7a3 100644
--- a/test/write_grids.test.js
+++ b/test/write_grids.test.js
@@ -1,7 +1,6 @@
 process.env.NODE_ENV = 'test';
 
 var fs = require('fs');
-var assert = require('assert');
 var MBTiles = require('..');
 
 var fixtureDir = __dirname + '/fixtures/output';
@@ -10,7 +9,7 @@ var fixtureDir = __dirname + '/fixtures/output';
 try { fs.unlinkSync(fixtureDir + '/write_2.mbtiles'); } catch(err) {}
 try { fs.mkdirSync(fixtureDir, 0755); } catch(err) {}
 
-exports['test mbtiles file creation'] = function(beforeExit) {
+exports['test mbtiles file creation'] = function(beforeExit, assert) {
     var completed = { written: 0, read: 0 };
     new MBTiles(fixtureDir + '/write_2.mbtiles', function(err, mbtiles) {
         completed.open = true;