Delete a normal file.
function testSingleFile() {
// Create a file for testing
$filepath = file_default_scheme() . '://' . $this
->randomName();
file_put_contents($filepath, '');
// Delete the file.
$this
->assertTrue(file_unmanaged_delete_recursive($filepath), 'Function reported success.');
$this
->assertFalse(file_exists($filepath), 'Test file has been deleted.');
}