diff --git a/tests/unit/framework/helpers/FileHelperTest.php b/tests/unit/framework/helpers/FileHelperTest.php
index df27819..896218e 100644
--- a/tests/unit/framework/helpers/FileHelperTest.php
+++ b/tests/unit/framework/helpers/FileHelperTest.php
@@ -169,7 +169,7 @@ class FileHelperTest extends TestCase
 		$this->assertFileMode($fileMode, $dstDirName . DIRECTORY_SEPARATOR . $fileName, 'Copied file has wrong mode!');
 	}
 
-	public function stestRemoveDirectory()
+	public function testRemoveDirectory()
 	{
 		$dirName = 'test_dir_for_remove';
 		$this->createFileStructure(array(
@@ -189,6 +189,9 @@ class FileHelperTest extends TestCase
 		FileHelper::removeDirectory($dirName);
 
 		$this->assertFalse(file_exists($dirName), 'Unable to remove directory!');
+
+		// should be silent about non-existing directories
+		FileHelper::removeDirectory($basePath . DIRECTORY_SEPARATOR . 'nonExisting');
 	}
 
 	public function testFindFiles()
@@ -272,8 +275,9 @@ class FileHelperTest extends TestCase
 	{
 		$basePath = $this->testFilePath;
 		$dirName = $basePath . DIRECTORY_SEPARATOR . 'test_dir_level_1' . DIRECTORY_SEPARATOR . 'test_dir_level_2';
-		FileHelper::mkdir($dirName);
+		$this->assertTrue(FileHelper::mkdir($dirName), 'FileHelper::mkdir should return true if directory was created!');
 		$this->assertTrue(file_exists($dirName), 'Unable to create directory recursively!');
+		$this->assertTrue(FileHelper::mkdir($dirName), 'FileHelper::mkdir should return true for already existing directories!');
 	}
 
 	public function testGetMimeTypeByExtension()
@@ -292,4 +296,20 @@ class FileHelperTest extends TestCase
 			$this->assertEquals($mimeType, FileHelper::getMimeTypeByExtension($fileName, $magicFile));
 		}
 	}
+
+	public function testGetMimeType()
+	{
+		$file = $this->testFilePath . DIRECTORY_SEPARATOR . 'mime_type_test.txt';
+		file_put_contents($file, 'some text');
+		$this->assertEquals('text/plain', FileHelper::getMimeType($file));
+
+		$file = $this->testFilePath . DIRECTORY_SEPARATOR . 'mime_type_test.json';
+		file_put_contents($file, '{"a": "b"}');
+		$this->assertEquals('text/plain', FileHelper::getMimeType($file));
+	}
+
+	public function testNormalizePath()
+	{
+		$this->assertEquals(DIRECTORY_SEPARATOR.'home'.DIRECTORY_SEPARATOR.'demo', FileHelper::normalizePath('/home\demo/'));
+	}
 }