Fix single dataset test.

The "two pool, one metic" test was only passing because of previous calls to Gather() had already populated the values.

plugins/zfs/zfs_test.go

@@ -195,7 +195,7 @@ func TestZfsGeneratesMetrics(t *testing.T) {
  err = ioutil.WriteFile(testKstatPath+"/vdev_cache_stats", []byte(vdev_cache_statsContents), 0644)
  require.NoError(t, err)
 
- intMetrics := getKstatMetrics()
+ intMetrics := getKstatMetricsAll()
 
  var acc testutil.Accumulator
 
@@ -225,6 +225,7 @@ func TestZfsGeneratesMetrics(t *testing.T) {
  }
 
  z = &Zfs{KstatPath: testKstatPath}
+ acc = testutil.Accumulator{}
  err = z.Gather(&acc)
  require.NoError(t, err)
 
@@ -233,8 +234,11 @@ func TestZfsGeneratesMetrics(t *testing.T) {
  assert.True(t, acc.CheckTaggedValue(metric.name, metric.value, tags))
  }
 
+ intMetrics = getKstatMetricsArcOnly()
+
  //two pools, one metric
  z = &Zfs{KstatPath: testKstatPath, KstatMetrics: []string{"arcstats"}}
+ acc = testutil.Accumulator{}
  err = z.Gather(&acc)
  require.NoError(t, err)
 
@@ -247,7 +251,7 @@ func TestZfsGeneratesMetrics(t *testing.T) {
  require.NoError(t, err)
 }
 
-func getKstatMetrics() []*metrics {
+func getKstatMetricsArcOnly() []*metrics {
  return []*metrics{
  {
  name: "arcstats_hits",
@@ -593,6 +597,11 @@ func getKstatMetrics() []*metrics {
  name: "arcstats_arc_meta_max",
  value: 18327165696,
  },
+ }
+}
+
+func getKstatMetricsAll() []*metrics {
+ otherMetrics := []*metrics{
  {
  name: "zfetchstats_hits",
  value: 7812959060,
@@ -650,6 +659,8 @@ func getKstatMetrics() []*metrics {
  value: 0,
  },
  }
+
+ return append(getKstatMetricsArcOnly(), otherMetrics...)
 }
 
 func getPoolMetrics() []*metrics {