diff --git a/Scisr.php b/Scisr.php
index 4a26a88..7e05764 100644
--- a/Scisr.php
+++ b/Scisr.php
@@ -106,9 +106,11 @@ public function setOutput($output)
         $this->_output = $output;
     }
 
-    public static function createScisr($className = 'Scisr')
+    public static function createScisr($className = 'Scisr', $db = null)
     {
-        $db = Scisr_Db::getDb();
+        if ($db === null) {
+            $db = Scisr_Db::getDb();
+        }
         $dbFiles = new Scisr_Db_Files($db);
         $dbFiles->init();
         $dbFileIncludes = new Scisr_Db_FileIncludes($db);
diff --git a/tests/FileCachingTest.php b/tests/FileCachingTest.php
index a772be9..ff864a7 100644
--- a/tests/FileCachingTest.php
+++ b/tests/FileCachingTest.php
@@ -55,7 +55,7 @@ public function testDontUseIncompleteCacheResults() {
 include "Foo.php"
 EOL;
         $this->populateFile($code);
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClassFile('Foo', 'Bar');
         $s->addFile($this->test_file);
         $s->run();
diff --git a/tests/RenameClassFileSystemTest.php b/tests/RenameClassFileSystemTest.php
index 74aaa04..d25c12b 100644
--- a/tests/RenameClassFileSystemTest.php
+++ b/tests/RenameClassFileSystemTest.php
@@ -9,7 +9,7 @@ class RenameClassFileSystemTest extends Scisr_Tests_MultipleFileTestCase
     public function testRenameClassFileAndCompareFile($oldName, $newName, $oldFile, $newFile) {
         $this->populateDir(dirname(__FILE__) . '/_files/classFileFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClassFile($oldName, $newName);
         $s->addFile($this->test_dir . '/' . $oldFile);
         $s->run();
@@ -28,7 +28,7 @@ public function classFileProvider() {
     public function testDontRenameClassFileWithoutAllowedExtension() {
         $this->populateDir(dirname(__FILE__) . '/_files/classFileFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClassFile('MyOtherClass', 'NewClass');
         $s->setAllowedFileExtensions(array('php'));
         $s->addFile($this->test_dir);
@@ -41,7 +41,7 @@ public function testDontRenameClassFileWithoutAllowedExtension() {
     public function testRenameClassFileWithFunnyExtension() {
         $this->populateDir(dirname(__FILE__) . '/_files/classFileFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClassFile('StrangeClass', 'StrangeQuark');
         $s->setAllowedFileExtensions(array('php', 'foo'));
         $s->addFile($this->test_dir);
@@ -53,7 +53,7 @@ public function testRenameClassFileWithFunnyExtension() {
     public function testRenameDirWithNamespacing() {
         $this->populateDir(dirname(__FILE__) . '/_files/classFileNamespacedFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClassFile('Foo_Bar_Quark', 'Foo_Baz_Quack');
         $s->addFile($this->test_dir);
         $s->run();
@@ -64,7 +64,7 @@ public function testRenameDirWithNamespacing() {
     public function testDontCreateDirNamespacingIfOriginalIsnt() {
         $this->populateDir(dirname(__FILE__) . '/_files/classFileNamespacedFixture2', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClassFile('Foo_Bar_Quark', 'Foo_Baz_Quack');
         $s->addFile($this->test_dir);
         $s->run();
@@ -75,7 +75,7 @@ public function testDontCreateDirNamespacingIfOriginalIsnt() {
     public function testRenameClassFileAndCompareDir() {
         $this->populateDir(dirname(__FILE__) . '/_files/classFileFixture-dir', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClassFile('Foo', 'Baz');
         $s->addFile($this->test_dir);
         $s->run();
diff --git a/tests/RenameClassFileTest.php b/tests/RenameClassFileTest.php
index d7f5789..d75f694 100644
--- a/tests/RenameClassFileTest.php
+++ b/tests/RenameClassFileTest.php
@@ -7,7 +7,7 @@ class RenameClassFileTest extends Scisr_SingleFileTest
     public function renameAndCompare($original, $expected, $oldname='Foo', $newname='Baz', $oldfile='Foo.php', $newfile='Baz.php', $aggressive=false) {
         $this->populateFile($original);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         if ($aggressive) {
             $s->setEditMode(Scisr::MODE_AGGRESSIVE);
         }
diff --git a/tests/RenameClassSystemTest.php b/tests/RenameClassSystemTest.php
index 21cee7a..f6b261f 100644
--- a/tests/RenameClassSystemTest.php
+++ b/tests/RenameClassSystemTest.php
@@ -7,7 +7,7 @@ class RenameClassSystemTest extends Scisr_Tests_MultipleFileTestCase
     public function testRenameClassAndCompareFile() {
         $this->populateDir(dirname(__FILE__) . '/_files/cliFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClass('Foo', 'Baz');
         $s->addFile($this->test_dir . '/test.php');
         $s->run();
@@ -18,7 +18,7 @@ public function testRenameClassAndCompareFile() {
     public function testRenameClassAndCompareFileWithRelativeDir() {
         $this->populateDir(dirname(__FILE__) . '/_files/cliFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClass('Foo', 'Baz');
         $s->addFile($this->rel_test_dir . '/test.php');
         $s->run();
@@ -29,7 +29,7 @@ public function testRenameClassAndCompareFileWithRelativeDir() {
     public function testRenameClassAndCompareDir() {
         $this->populateDir(dirname(__FILE__) . '/_files/cliFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClass('Foo', 'Baz');
         $s->addFile($this->test_dir);
         $s->run();
diff --git a/tests/RenameClassTest.php b/tests/RenameClassTest.php
index e14bf35..7040b70 100644
--- a/tests/RenameClassTest.php
+++ b/tests/RenameClassTest.php
@@ -7,7 +7,7 @@ class RenameClassTest extends Scisr_SingleFileTest
     public function renameAndCompare($original, $expected, $oldname='Foo', $newname='Baz', $aggressive=false) {
         $this->populateFile($original);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         if ($aggressive) {
             $s->setEditMode(Scisr::MODE_AGGRESSIVE);
         }
diff --git a/tests/RenameFileSystemTest.php b/tests/RenameFileSystemTest.php
index 4d693e2..5485daf 100644
--- a/tests/RenameFileSystemTest.php
+++ b/tests/RenameFileSystemTest.php
@@ -40,7 +40,7 @@ public function testRenameFileWithRelativePath() {
     public function testDontMoveFileInTimidMode() {
         $this->populateDir(dirname(__FILE__) . '/_files/renameFileFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setEditMode(Scisr::MODE_TIMID);
         $s->setRenameFile($this->test_dir . '/test2.php', $this->test_dir . '/otherfolder/things.php');
         $s->addFile($this->test_dir);
@@ -84,7 +84,7 @@ public function testRenameFileAltersIncludesSwitchPlaces() {
     }
 
 	public function doRenameFile($old, $new) {
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameFile($old, $new);
         $s->addFile($this->test_dir);
         $s->run();
diff --git a/tests/RenameFileTest.php b/tests/RenameFileTest.php
index 11764df..bf0170a 100644
--- a/tests/RenameFileTest.php
+++ b/tests/RenameFileTest.php
@@ -7,7 +7,7 @@ class RenameFileTest extends Scisr_SingleFileTest
     public function renameAndCompare($original, $expected, $oldname='Foo.php', $newname='Baz.php', $aggressive=false) {
         $this->populateFile($original);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         if ($aggressive) {
             $s->setEditMode(Scisr::MODE_AGGRESSIVE);
         }
diff --git a/tests/RenameMethodSystemTest.php b/tests/RenameMethodSystemTest.php
index 2174d08..a690879 100644
--- a/tests/RenameMethodSystemTest.php
+++ b/tests/RenameMethodSystemTest.php
@@ -7,7 +7,7 @@ class RenameMethodSystemTest extends Scisr_Tests_MultipleFileTestCase
     public function testRenameMethodAndCompareFile() {
         $this->populateDir(dirname(__FILE__) . '/_files/cliFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameMethod('Foo', 'bar', 'quark', false);
         $s->addFile($this->test_dir . '/test.php');
         $s->run();
@@ -18,7 +18,7 @@ public function testRenameMethodAndCompareFile() {
     public function testRenameMethodAndCompareDir() {
         $this->populateDir(dirname(__FILE__) . '/_files/cliFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameMethod('Foo', 'bar', 'quark', false);
         $s->addFile($this->test_dir);
         $s->run();
@@ -29,7 +29,7 @@ public function testRenameMethodAndCompareDir() {
     public function testRenameMethodWithIncludedFile() {
         $this->populateDir(dirname(__FILE__) . '/_files/renameMethodWithIncludesFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameMethod('Foo', 'bar', 'baz', false);
         $s->addFile($this->test_dir);
         $s->run();
@@ -40,7 +40,7 @@ public function testRenameMethodWithIncludedFile() {
     public function testClassInclusionOrder() {
         $this->populateDir(dirname(__FILE__) . '/_files/renameMethodWithClassFixture', $this->test_dir);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameMethod('Foo', 'bar', 'baz', false);
         // We want to force an ordering here
         $s->addFile($this->test_dir . '/a.php');
diff --git a/tests/RenameMethodTest.php b/tests/RenameMethodTest.php
index c48064a..6ebac0e 100644
--- a/tests/RenameMethodTest.php
+++ b/tests/RenameMethodTest.php
@@ -7,7 +7,7 @@ class RenameMethodTest extends Scisr_SingleFileTest
     public function renameAndCompare($original, $expected, $class='Foo', $oldmethod='bar', $newmethod='baz', $aggressive=false, $inheritance=false) {
         $this->populateFile($original);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         if ($aggressive) {
             $s->setEditMode(Scisr::MODE_AGGRESSIVE);
         }
@@ -1427,7 +1427,7 @@ public function testIncludeFileWhenClassUsedStatically() {
     private function renameAndCompareWithIncludes($orig, $expected, $includedFile) {
         $this->populateFile($orig);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $sniffer = new MockSniffer($s->getFactory()->getCollaborator('Scisr_Db_Classes'), $s->getFactory()->getCollaborator('Scisr_Db_VariableTypes'));
         $sniffer->incFile = $includedFile;
         $sniffer->test_file = $this->test_file;
diff --git a/tests/ScisrSingleFileTest.php b/tests/ScisrSingleFileTest.php
index 993d51f..74b0612 100644
--- a/tests/ScisrSingleFileTest.php
+++ b/tests/ScisrSingleFileTest.php
@@ -7,12 +7,12 @@ class ScisrTest extends Scisr_SingleFileTest
     public function parseCode($code) {
         $this->populateFile($code);
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameClass('dummy', 'dummy2');
         $s->addFile($this->test_file);
         $s->run();
 
-        $s = Scisr::createScisr();
+        $s = $this->getScisr();
         $s->setRenameMethod('DummyClass', 'dummy', 'dummy2', false);
         $s->addFile($this->test_file);
         $s->run();
diff --git a/tests/Scisr_TestCase.php b/tests/Scisr_TestCase.php
index c91b997..0b7868b 100644
--- a/tests/Scisr_TestCase.php
+++ b/tests/Scisr_TestCase.php
@@ -6,14 +6,22 @@ class Scisr_TestCase extends PHPUnit_Framework_TestCase
 {
 
     public function setUp() {
-        Scisr_Db::clearDb();
         chdir(dirname(__FILE__));
     }
 
     public function tearDown() {
-        Scisr_Db::clearDb();
         Scisr_ChangeRegistry::clearAll();
         chdir(dirname(__FILE__));
     }
 
+    public function getDb()
+    {
+        return new PDO('sqlite::memory:');
+    }
+
+    public function getScisr($className = 'Scisr')
+    {
+        return Scisr::createScisr($className, $this->getDb());
+    }
+
 }