Adding tests for 4 byte unicode characters

* success on SQLite and Postgres
* failure on MySQL due to the limited charset that only supports up to 3 bytes

tests/data/db_structure.xml

@@ -293,4 +293,19 @@
 
 	</table>
 
+  <table>
+
+		<name>*dbprefix*text_table</name>
+		<declaration>
+
+         <field>
+          <name>textfield</name>
+          <type>text</type>
+          <notnull>false</notnull>
+          <length>255</length>
+         </field>
+
+		</declaration>
+  </table>
+
 </database>

tests/lib/DB/LegacyDBTest.php

@@ -46,6 +46,11 @@ class LegacyDBTest extends \Test\TestCase {
 	 */
 	private $table5;
 
+	/**
+	 * @var string
+	 */
+	private $text_table;
+
 	protected function setUp() {
 		parent::setUp();
 
@@ -63,6 +68,7 @@ class LegacyDBTest extends \Test\TestCase {
 		$this->table3 = $this->test_prefix.'vcategory';
 		$this->table4 = $this->test_prefix.'decimal';
 		$this->table5 = $this->test_prefix.'uniconst';
+		$this->text_table = $this->test_prefix.'text_table';
 	}
 
 	protected function tearDown() {
@@ -390,4 +396,29 @@ class LegacyDBTest extends \Test\TestCase {
 		$result = $query->execute(array('%ba%'));
 		$this->assertCount(1, $result->fetchAll());
 	}
+
+	/**
+	 * @dataProvider insertAndSelectDataProvider
+	 */
+	public function testInsertAndSelectData($expected) {
+		$table = "*PREFIX*{$this->text_table}";
+
+		$query = OC_DB::prepare("INSERT INTO `$table` (`textfield`) VALUES (?)");
+		$result = $query->execute(array($expected));
+		$this->assertEquals(1, $result);
+
+		$actual = OC_DB::prepare("SELECT `textfield` FROM `$table`")->execute()->fetchOne();
+		$this->assertSame($expected, $actual);
+	}
+
+	public function insertAndSelectDataProvider() {
+		return [
+			['abcdefghijklmnopqrstuvwxyzABCDEFGHIKLMNOPQRSTUVWXYZ'],
+			['0123456789'],
+			['äöüÄÖÜß!"§$%&/()=?#\'+*~°^`´'],
+			['²³¼½¬{[]}\\'],
+			['♡⚗'],
+			['💩'], # :hankey: on github
+		];
+	}
 }