diff --git a/4dev/tests/CoreLibsCheckFileTest.php b/4dev/tests/CoreLibsCheckFileTest.php
index c59c9199..57e618c0 100644
--- a/4dev/tests/CoreLibsCheckFileTest.php
+++ b/4dev/tests/CoreLibsCheckFileTest.php
@@ -8,32 +8,81 @@ use PHPUnit\Framework\TestCase;
 
 /**
  * Undocumented class
- * @testdox CoreLibs\Convert\Math method tests
+ * @testdox CoreLibs\Check\File method tests
  */
 final class CoreLibsCheckFileTest extends TestCase
 {
+	/** @var array<mixed> */
+	private $files = [];
+
 	protected function setUp(): void
 	{
-		// write a dummy file for testing
+		// write a dummy files for testing
 	}
 
 	protected function tearDown(): void
 	{
-		// unlink file
+		// unlink files
 	}
 
-	public function testGetFilenameEnding(string $input, string $expected): void
+	/**
+	 * main file list + data provider
+	 *
+	 * @return array
+	 */
+	public function filesList(): array
+	{
+		return [
+			['filename.txt', 'txt', 5]
+		];
+	}
+
+	public function filesExtensionProvider(): array
+	{
+		$list = [];
+		foreach ($this->filesList as $row) {
+			$list[$row[0] . ' must be extension ' . $row[1]] = [$row[0], $row[1]];
+		}
+		return $list;
+	}
+
+	/**
+	 * Undocumented function
+	 *
+	 * @#dataProvider filesExtensionProvider
+	 * @#testdox File::getFilenameEnding Input $input must be $expected
+	 * //string $input, string $expected
+	 *
+	 * @param string $input
+	 * @param string $expected
+	 * @return void
+	 */
+	public function testGetFilenameEnding(): void
 	{
 		// getFilenameEnding
-		$this->assertEquals(
+		/* $this->assertEquals(
 			$expected,
 			\CoreLibs\Check\File::getFilenameEnding($input)
+		); */
+		$this->assertTrue(true, 'This should already work.');
+		$this->markTestIncomplete(
+			'testGetFilenameEnding has not been implemented yet.'
 		);
 	}
 
+	/**
+	 * Undocumented function
+	 * // string $input, string $expected
+	 *
+	 * @return void
+	 */
 	public function testGetLinesFromFile(): void
 	{
 		// getLinesFromFile
+		$this->assertTrue(true, 'This should already work.');
+		$this->markTestIncomplete(
+			'testGetLinesFromFile has not been implemented yet.'
+		);
 	}
 }