def METHOD_NAME():
    client.load('post_variables')
    resp = client.post(
        headers={
            'Host': 'localhost',
            'Content-Type': 'application/x-www-form-urlencoded',
            'Connection': 'close',
        },
        body='var1=val1&var2=&var3',
    )
    assert resp['headers']['X-Var-1'] == 'val1', 'POST variables'
    assert resp['headers']['X-Var-2'] == '', 'POST variables 2'
    assert resp['headers']['X-Var-3'] == '', 'POST variables 3'