@Test
public void testExecute() throws Exception
{

    doReturn( true ).when( topology ).exchangeSshKeys();
    doReturn( TestHelper.SSH_KEYS() ).when( step ).readOrCreateSshKeys();
    step.execute();
    verify( step ).exchangeSshKeys( anySet() );
    doReturn( true ).when( topology ).exchangeSshKeys();
    step.execute();
    verify( step, atLeastOnce() ).appendSshKeys( isA( SshKeys.class ) );
}