def METHOD_NAME(self, mocker):
    """Test impressions posting API call."""
    httpclient = mocker.Mock(spec=client.HttpClient)
    httpclient.post.return_value = client.HttpResponse(200, '')
    cfg = DEFAULT_CONFIG.copy()
    cfg.update({'IPAddressesEnabled': False})
    sdk_metadata = get_metadata(cfg)
    impressions_api = impressions.ImpressionsAPI(httpclient, 'some_api_key', sdk_metadata, mocker.Mock(), ImpressionsMode.DEBUG)
    response = impressions_api.flush_impressions(self.impressions)
    call_made = httpclient.post.mock_calls[0]
    # validate positional arguments
    assert call_made[1] == ('events', '/testImpressions/bulk', 'some_api_key')
    # validate key-value args (headers)
    assert call_made[2]['extra_headers'] == {
        'SplitSDKVersion': 'python-%s' % __version__,
        'SplitSDKImpressionsMode': 'DEBUG'
    }
    # validate key-value args (body)
    assert call_made[2]['body'] == self.expectedImpressions