Prose\ExpectsGraphite::metricSumIs PHP Method

    public function metricSumIs($metric, $expectedTotal, $startTime, $endTime)
    {
        // when are we looking for?
        $humanStartTime = date('Y-m-d H:i:s', $startTime);
        $humanEndTime = date('Y-m-d H:i:s', $endTime);
        // what are we doing?
        $log = usingLog()->startAction("ensure metric '{$metric}' sums to '{$expectedTotal}' between '{$humanStartTime}' and '{$humanEndTime}'");
        // get the data from graphite
        $data = fromGraphite()->getDataFor($metric, $startTime, $endTime);
        // do we *have* any data?
        if (empty($data) || !isset($data[0]->target, $data[0]->datapoints)) {
            // graphite returns an empty data set when there is no data
            //
            // NOTE: this can also happen when the test is asking for
            //       the wrong metric :(
            if ($expectedTotal !== 0) {
                // we were expecting there to be some data
                throw new E5xx_ExpectFailed(__METHOD__, "data available for metric '{$metric}'", "no data available for metric '{$metric}'");
            }
            // if we get here, it's reasonable to assume that everything is
            // as it should be
            $log->endAction("no data available for metric '{$metric}'; assuming success");
            return;
        }
        // we have data ... let's make sure we're happy with it
        $actualTotal = 0;
        foreach ($data[0]->datapoints as $datapoint) {
            if ($datapoint[0] !== null) {
                $actualTotal += $datapoint[0];
            }
        }
        // do we have the total we expected?
        assertsDouble($actualTotal)->equals($expectedTotal);
        // all done
        $log->endAction("data was available, metric '{$metric}' sums to '{$actualTotal}'");
        return;
    }