test: file: Check that directories are not treated as files

Directories can not be opened as a file, so the exists() check should
not return true for a path which points to a directory.

Directories are not handled by the File class.

Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

test/file.cpp

@@ -49,6 +49,11 @@ protected:
 			return TestFail;
 		}
 
+		if (File::exists("/dev")) {
+			cerr << "Directories should not be treated as files" << endl;
+			return TestFail;
+		}
+
 		/* Test unnamed file. */
 		File file;