Test that file_save_data() fails overwriting an existing file.
function testExistingError() {
$contents = $this
->randomName(8);
$existing = $this
->createFile(NULL, $contents);
// Check the overwrite error.
$result = file_save_data('asdf', $existing->uri, FILE_EXISTS_ERROR);
$this
->assertFalse($result, 'Overwriting a file fails when FILE_EXISTS_ERROR is specified.');
$this
->assertEqual($contents, file_get_contents($existing->uri), 'Contents of existing file were unchanged.');
// Check that no hooks were called while failing.
$this
->assertFileHooksCalled(array());
// Ensure that the existing file wasn't overwritten.
$this
->assertFileUnchanged($existing, file_load($existing->fid, TRUE));
}