gistfile1.php

function testFileCreate() {
    $text_file = current($this->drupalGetTestFiles('text'));

    $file = new stdClass();
    $realpath = realpath($text_file->filename);
    $file->filesize = filesize($realpath);
    $file->filepath = 'sites/default/files/' . $text_file->basename;

    $fh = fopen($realpath, 'r');
    $file_data = fread($fh, $file->filesize);
    fclose($fh);

    $file->file = base64_encode($file_data);

    $response = $this->servicesPost($this->endpoint->path . '/file', array('file' => $file));
}

POST DATA: