diff --git a/core/tests/Drupal/Tests/Core/Database/ConnectionTest.php b/core/tests/Drupal/Tests/Core/Database/ConnectionTest.php
new file mode 100644
index 00000000000..20667ee211c
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Database/ConnectionTest.php
@@ -0,0 +1,326 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\Tests\Core\Database\ConnectionTest.
+ */
+
+namespace Drupal\Tests\Core\Database;
+
+use Drupal\Tests\Core\Database\Stub\StubConnection;
+use Drupal\Tests\Core\Database\Stub\StubPDO;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests Drupal\Core\Database\Connection.
+ *
+ * @group Drupal
+ * @group Database
+ */
+class ConnectionTest extends UnitTestCase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getInfo() {
+    return array(
+      'name' => 'Connection Test',
+      'description' => 'Test the Connection class.',
+      'group' => 'Database',
+    );
+  }
+
+  /**
+   * Dataprovider for testPrefixRoundTrip().
+   *
+   * @return array
+   *   Array of arrays with the following elements:
+   *   - Arguments to pass to Connection::setPrefix().
+   *   - Expected result from Connection::tablePrefix().
+   */
+  public function providerPrefixRoundTrip() {
+    return array(
+      array(
+        array('' => 'test_'),
+        'test_',
+      ),
+      array(
+        array(
+          'fooTable' => 'foo_',
+          'barTable' => 'bar_',
+        ),
+        array(
+          'fooTable' => 'foo_',
+          'barTable' => 'bar_',
+        ),
+      ),
+    );
+  }
+
+  /**
+   * Exercise setPrefix() and tablePrefix().
+   *
+   * @dataProvider providerPrefixRoundTrip
+   */
+  public function testPrefixRoundTrip($expected, $prefix_info) {
+    $mock_pdo = $this->getMock('Drupal\Tests\Core\Database\Stub\StubPDO');
+    $connection = new StubConnection($mock_pdo, array());
+
+    // setPrefix() is protected, so we make it accessible with reflection.
+    $reflection = new \ReflectionClass('Drupal\Tests\Core\Database\Stub\StubConnection');
+    $set_prefix = $reflection->getMethod('setPrefix');
+    $set_prefix->setAccessible(TRUE);
+
+    // Set the prefix data.
+    $set_prefix->invokeArgs($connection, array($prefix_info));
+    // Check the round-trip.
+    foreach ($expected as $table => $prefix) {
+      $this->assertEquals($prefix, $connection->tablePrefix($table));
+    }
+  }
+
+  /**
+   * Dataprovider for testPrefixTables().
+   *
+   * @return array
+   *   Array of arrays with the following elements:
+   *   - Expected result.
+   *   - Table prefix.
+   *   - Query to be prefixed.
+   */
+  public function providerTestPrefixTables() {
+    return array(
+      array(
+        'SELECT * FROM test_table',
+        'test_',
+        'SELECT * FROM {table}',
+      ),
+      array(
+        'SELECT * FROM first_table JOIN second_thingie',
+        array(
+          'table' => 'first_',
+          'thingie' => 'second_',
+        ),
+        'SELECT * FROM {table} JOIN {thingie}',
+      ),
+    );
+  }
+
+  /**
+   * Exercise the prefixTables() method.
+   *
+   * @dataProvider providerTestPrefixTables
+   */
+  public function testPrefixTables($expected, $prefix_info, $query) {
+    $mock_pdo = $this->getMock('Drupal\Tests\Core\Database\Stub\StubPDO');
+    $connection = new StubConnection($mock_pdo, array('prefix' => $prefix_info));
+    $this->assertEquals($expected, $connection->prefixTables($query));
+  }
+
+  /**
+   * Dataprovider for testEscapeMethods().
+   *
+   * @return array
+   *   Array of arrays with the following elements:
+   *   - Expected escaped string.
+   *   - String to escape.
+   */
+  public function providerEscapeMethods() {
+    return array(
+      array('thing', 'thing'),
+      array('_item', '_item'),
+      array('item_', 'item_'),
+      array('_item_', '_item_'),
+      array('', '!@#$%^&*()-=+'),
+      array('123', '!1@2#3'),
+    );
+  }
+
+  /**
+   * Test the various escaping methods.
+   *
+   * All tested together since they're basically the same method
+   * with different names.
+   *
+   * @dataProvider providerEscapeMethods
+   * @todo Separate test method for each escape method?
+   */
+  public function testEscapeMethods($expected, $name) {
+    $mock_pdo = $this->getMock('Drupal\Tests\Core\Database\Stub\StubPDO');
+    $connection = new StubConnection($mock_pdo, array());
+    $this->assertEquals($expected, $connection->escapeDatabase($name));
+    $this->assertEquals($expected, $connection->escapeTable($name));
+    $this->assertEquals($expected, $connection->escapeField($name));
+    $this->assertEquals($expected, $connection->escapeAlias($name));
+  }
+
+  /**
+   * Dataprovider for testGetDriverClass().
+   *
+   * @return array
+   *   Array of arrays with the following elements:
+   *   - Expected namespaced class name.
+   *   - Driver.
+   *   - Namespace.
+   *   - Class name without namespace.
+   */
+  public function providerGetDriverClass() {
+    return array(
+      array(
+        'nonexistent_class',
+        'stub',
+        '\\',
+        'nonexistent_class',
+      ),
+      array(
+        'Drupal\\Core\\Database\\Driver\\mysql\\Select',
+        'mysql',
+        NULL,
+        'Select',
+      ),
+      array(
+        'Drupal\\Tests\\Core\\Database\\Stub\\Driver\\Schema',
+        'stub',
+        'Drupal\\Tests\\Core\\Database\\Stub\\Driver',
+        'Schema',
+      ),
+    );
+  }
+
+  /**
+   * Test getDriverClass().
+   *
+   * @dataProvider providerGetDriverClass
+   */
+  public function testGetDriverClass($expected, $driver, $namespace, $class) {
+    $mock_pdo = $this->getMock('Drupal\Tests\Core\Database\Stub\StubPDO');
+    $connection = new StubConnection($mock_pdo, array('namespace' => $namespace));
+    // Set the driver using our stub class' public property.
+    $connection->driver = $driver;
+    $this->assertEquals($expected, $connection->getDriverClass($class));
+  }
+
+  /**
+   * Dataprovider for testSchema().
+   *
+   * @return array
+   *   Array of arrays with the following elements:
+   *   - Expected namespaced class of schema object.
+   *   - Driver for PDO connection.
+   *   - Namespace for connection.
+   */
+  public function providerSchema() {
+    return array(
+      array(
+        'Drupal\\Tests\\Core\\Database\\Stub\\Driver\\Schema',
+        'stub',
+        'Drupal\\Tests\\Core\\Database\\Stub\\Driver',
+      ),
+    );
+  }
+
+  /**
+   * Test Connection::schema().
+   *
+   * @dataProvider providerSchema
+   */
+  public function testSchema($expected, $driver, $namespace) {
+    $mock_pdo = $this->getMock('Drupal\Tests\Core\Database\Stub\StubPDO');
+    $connection = new StubConnection($mock_pdo, array('namespace' => $namespace));
+    $connection->driver = $driver;
+    $this->assertInstanceOf($expected, $connection->schema());
+  }
+
+  /**
+   * Test Connection::destroy().
+   */
+  public function testDestroy() {
+    $mock_pdo = $this->getMock('Drupal\Tests\Core\Database\Stub\StubPDO');
+    // Mocking StubConnection gives us access to the $schema attribute.
+    $connection = $this->getMock(
+      'Drupal\Tests\Core\Database\Stub\StubConnection',
+      NULL,
+      array($mock_pdo, array('namespace' => 'Drupal\\Tests\\Core\\Database\\Stub\\Driver'))
+    );
+    // Generate a schema object in order to verify that we've NULLed it later.
+    $this->assertInstanceOf(
+      'Drupal\\Tests\\Core\\Database\\Stub\\Driver\\Schema',
+      $connection->schema()
+    );
+    $connection->destroy();
+    $this->assertAttributeEquals(NULL, 'schema', $connection);
+  }
+
+  /**
+   * Dataprovider for testMakeComments().
+   *
+   * @return array
+   *   Array of arrays with the following elements:
+   *   - Expected filtered comment.
+   *   - Arguments for Connection::makeComment().
+   */
+  public function providerMakeComments() {
+    return array(
+      array(
+        '/*  */ ',
+        array(''),
+      ),
+      array(
+        '/* Exploit * / DROP TABLE node; -- */ ',
+        array('Exploit * / DROP TABLE node; --'),
+      ),
+      array(
+        '/* Exploit DROP TABLE node; --; another comment */ ',
+        array('Exploit */ DROP TABLE node; --', 'another comment'),
+      ),
+    );
+  }
+
+  /**
+   * Test Connection::makeComments().
+   *
+   * @dataProvider providerMakeComments
+   */
+  public function testMakeComments($expected, $comment_array) {
+    $mock_pdo = $this->getMock('Drupal\Tests\Core\Database\Stub\StubPDO');
+    $connection = new StubConnection($mock_pdo, array());
+    $this->assertEquals($expected, $connection->makeComment($comment_array));
+  }
+
+  /**
+   * Dataprovider for testFilterComments().
+   *
+   * @return array
+   *   Array of arrays with the following elements:
+   *   - Expected filtered comment.
+   *   - Comment to filter.
+   */
+  public function providerFilterComments() {
+    return array(
+      array('', ''),
+      array('Exploit * / DROP TABLE node; --', 'Exploit * / DROP TABLE node; --'),
+      array('Exploit DROP TABLE node; --', 'Exploit */ DROP TABLE node; --'),
+    );
+  }
+
+  /**
+   * Test Connection::filterComments().
+   *
+   * @dataProvider providerFilterComments
+   */
+  public function testFilterComments($expected, $comment) {
+    $mock_pdo = $this->getMock('Drupal\Tests\Core\Database\Stub\StubPDO');
+    $connection = new StubConnection($mock_pdo, array());
+
+    // filterComment() is protected, so we make it accessible with reflection.
+    $reflection = new \ReflectionClass('Drupal\Tests\Core\Database\Stub\StubConnection');
+    $filter_comment = $reflection->getMethod('filterComment');
+    $filter_comment->setAccessible(TRUE);
+
+    $this->assertEquals(
+      $expected,
+      $filter_comment->invokeArgs($connection, array($comment))
+    );
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Database/Stub/Driver/Schema.php b/core/tests/Drupal/Tests/Core/Database/Stub/Driver/Schema.php
new file mode 100644
index 00000000000..eb7f773d036
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Database/Stub/Driver/Schema.php
@@ -0,0 +1,18 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Database\Stub\Driver\Schema.
+ */
+
+namespace Drupal\Tests\Core\Database\Stub\Driver;
+
+/**
+ * A very minimal class for testing purposes.
+ *
+ * @see ConnectionTest::testGetDriverClass()
+ * @see ConnectionTest::testSchema()
+ */
+class Schema {
+  // No-op.
+}
diff --git a/core/tests/Drupal/Tests/Core/Database/Stub/StubConnection.php b/core/tests/Drupal/Tests/Core/Database/Stub/StubConnection.php
new file mode 100644
index 00000000000..d36a8d18aa5
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Database/Stub/StubConnection.php
@@ -0,0 +1,77 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Database\Stub\StubConnection.
+ */
+
+namespace Drupal\Tests\Core\Database\Stub;
+
+use Drupal\Core\Database\Connection;
+use Drupal\Core\Database\StatementEmpty;
+
+/**
+ * A stub of the abstract Connection class for testing purposes.
+ *
+ * Includes minimal implementations of Connection's abstract methods.
+ */
+class StubConnection extends Connection {
+
+  /**
+   * Public property so we can test driver loading mechanism.
+   *
+   * @var string
+   * @see driver().
+   */
+  public $driver = 'stub';
+
+  /**
+   * {@inheritdoc}
+   */
+  public function queryRange($query, $from, $count, array $args = array(), array $options = array()) {
+    return new StatementEmpty();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function queryTemporary($query, array $args = array(), array $options = array()) {
+    return '';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function driver() {
+    return $this->driver;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function databaseType() {
+    return 'stub';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function createDatabase($database) {
+    return;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function mapConditionOperator($operator) {
+    return NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function nextId($existing_id = 0) {
+    return 0;
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Database/Stub/StubPDO.php b/core/tests/Drupal/Tests/Core/Database/Stub/StubPDO.php
new file mode 100644
index 00000000000..c0ea2be2f23
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Database/Stub/StubPDO.php
@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Database\Stub\StubPDO.
+ */
+
+namespace Drupal\Tests\Core\Database\Stub;
+
+/**
+ * A stub of \PDO for testing purposes.
+ *
+ * We override the constructor method so that PHPUnit can mock the \PDO class.
+ * \PDO itself can't be mocked, so we have to create a subclass. This subclass
+ * is being used to unit test Connection, so we don't need a functional database
+ * but we do need a mock \PDO object.
+ *
+ * @see Drupal\Tests\Core\Database\ConnectionTest
+ * @see Drupal\Core\Database\Connection
+ * @see http://stackoverflow.com/questions/3138946/mocking-the-pdo-object-using-phpunit
+ */
+class StubPDO extends \PDO {
+
+  /**
+   * Construction method.
+   *
+   * We override this construction method with a no-op in order to mock \PDO
+   * under unit tests.
+   *
+   * @see http://stackoverflow.com/questions/3138946/mocking-the-pdo-object-using-phpunit
+   */
+  public function __construct() {
+    // No-op.
+  }
+
+}