You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: metrics_test.go
    path of file: ./repos/juju/worker/dbaccessor
    
    the code of the file until where you have to start completion: // Copyright 2023 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.


    
func (s *metricsSuite) TestMetricsAreCollected(c *gc.C) {
	collector := NewMetricsCollector()

	done := make(chan struct{})
	go func() {
		defer close(done)
		collector.DBDuration.WithLabelValues("foo", "success").Observe(0.1)
		collector.DBRequests.WithLabelValues("foo").Inc()
		collector.TxnRequests.WithLabelValues("foo").Inc()
	}()

	select {
	case <-done:
	case <-time.After(testing.ShortWait):
		c.Fatalf("timed out waiting for metrics to be collected")
	}

	expected := bytes.NewBuffer([]byte(`
# HELP juju_db_duration_seconds Total time spent in db requests.
# TYPE juju_db_duration_seconds histogram
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="0.005"} 0
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="0.01"} 0
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="0.025"} 0
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="0.05"} 0
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="0.1"} 1
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="0.25"} 1
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="0.5"} 1
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="1"} 1
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="2.5"} 1
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="5"} 1
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="10"} 1
juju_db_duration_seconds_bucket{namespace="foo",result="success",le="+Inf"} 1
juju_db_duration_seconds_sum{namespace="foo",result="success"} 0.1
juju_db_duration_seconds_count{namespace="foo",result="success"} 1
# HELP juju_db_requests_total Number of active db requests.
# TYPE juju_db_requests_total gauge
juju_db_requests_total{namespace="foo"} 1
# HELP juju_db_txn_requests_total Total number of txn requests including retries.
# TYPE juju_db_txn_requests_total counter
juju_db_txn_requests_total{namespace="foo"} 1
		`[1:]))

	err := testutil.CollectAndCompare(
		collector, expected,
		"juju_db_requests_total",
		"juju_db_duration_seconds",
		"juju_db_txn_requests_total",
	)
	if !c.Check(err, jc.ErrorIsNil) {
		c.Logf("\nerror:\n%v", err)
	}
}