diff --git a/head_test.go b/head_test.go
index 63f6da6f7..ea40ab811 100644
--- a/head_test.go
+++ b/head_test.go
@@ -16,7 +16,9 @@ package tsdb
 import (
 	"io/ioutil"
 	"math"
+	"math/rand"
 	"os"
+	"sort"
 	"testing"
 	"unsafe"
 
@@ -161,3 +163,219 @@ func TestNonDuplicateNaNDatapointsCausesAmendError(t *testing.T) {
 		t.Fatalf("Expected error amending sample, got: %s", err)
 	}
 }
+
+func TestHeadBlock_e2e(t *testing.T) {
+	numDatapoints := 1000
+	numRanges := 1000
+	timeInterval := int64(3)
+	// Create 8 series with 1000 data-points of different ranges and run queries.
+	lbls := [][]labels.Label{
+		{
+			{"a", "b"},
+			{"instance", "localhost:9090"},
+			{"job", "prometheus"},
+		},
+		{
+			{"a", "b"},
+			{"instance", "127.0.0.1:9090"},
+			{"job", "prometheus"},
+		},
+		{
+			{"a", "b"},
+			{"instance", "127.0.0.1:9090"},
+			{"job", "prom-k8s"},
+		},
+		{
+			{"a", "b"},
+			{"instance", "localhost:9090"},
+			{"job", "prom-k8s"},
+		},
+		{
+			{"a", "c"},
+			{"instance", "localhost:9090"},
+			{"job", "prometheus"},
+		},
+		{
+			{"a", "c"},
+			{"instance", "127.0.0.1:9090"},
+			{"job", "prometheus"},
+		},
+		{
+			{"a", "c"},
+			{"instance", "127.0.0.1:9090"},
+			{"job", "prom-k8s"},
+		},
+		{
+			{"a", "c"},
+			{"instance", "localhost:9090"},
+			{"job", "prom-k8s"},
+		},
+	}
+
+	seriesMap := map[string][]sample{}
+	for _, l := range lbls {
+		seriesMap[labels.New(l...).String()] = []sample{}
+	}
+
+	tmpdir, _ := ioutil.TempDir("", "test")
+	defer os.RemoveAll(tmpdir)
+
+	hb, err := createHeadBlock(tmpdir+"/hb", 0, nil, 0, 1000)
+	require.NoError(t, err)
+	app := hb.Appender()
+
+	for _, l := range lbls {
+		ls := labels.New(l...)
+		series := seriesMap[labels.New(l...).String()]
+
+		ts := rand.Int63n(300)
+		for i := 0; i < numDatapoints; i++ {
+			v := rand.Float64()
+			series = append(series, sample{ts, v})
+
+			_, err := app.Add(ls, ts, v)
+			require.NoError(t, err)
+
+			ts += rand.Int63n(timeInterval) + 1
+		}
+
+		seriesMap[labels.New(l...).String()] = series
+	}
+
+	require.NoError(t, app.Commit())
+
+	// Query each selector on 1000 random time-ranges.
+	queries := []struct {
+		ms []labels.Matcher
+	}{
+		{
+			ms: []labels.Matcher{labels.NewEqualMatcher("a", "b")},
+		},
+		{
+			ms: []labels.Matcher{
+				labels.NewEqualMatcher("a", "b"),
+				labels.NewEqualMatcher("job", "prom-k8s"),
+			},
+		},
+		{
+			ms: []labels.Matcher{
+				labels.NewEqualMatcher("a", "c"),
+				labels.NewEqualMatcher("instance", "localhost:9090"),
+				labels.NewEqualMatcher("job", "prometheus"),
+			},
+		},
+		// TODO: Add Regexp Matchers.
+	}
+
+	for _, qry := range queries {
+		matched := []labels.Labels{}
+	Outer:
+		for _, ls := range lbls {
+			for _, m := range qry.ms {
+				if !matchLSet(m, ls) {
+					continue Outer
+				}
+			}
+
+			matched = append(matched, ls)
+		}
+
+		sort.Slice(matched, func(i, j int) bool {
+			return labels.Compare(matched[i], matched[j]) < 0
+		})
+
+		for i := 0; i < numRanges; i++ {
+			mint := rand.Int63n(300)
+			maxt := mint + rand.Int63n(timeInterval*int64(numDatapoints))
+
+			q := hb.Querier(mint, maxt)
+			ss := q.Select(qry.ms...)
+
+			// Build the mockSeriesSet.
+			matchedSeries := make([]Series, 0, len(matched))
+			for _, m := range matched {
+				smpls := boundedSamples(seriesMap[m.String()], mint, maxt)
+
+				// Only append those series for which samples exist as mockSeriesSet
+				// doesn't skip series with no samples.
+				// TODO: But sometimes SeriesSet returns an empty SeriesIterator
+				if len(smpls) > 0 {
+					matchedSeries = append(matchedSeries, newSeries(
+						m.Map(),
+						smpls,
+					))
+				}
+			}
+			expSs := newListSeriesSet(matchedSeries)
+
+			// Compare both SeriesSets.
+			for {
+				eok, rok := expSs.Next(), ss.Next()
+
+				// HACK: Skip a series if iterator is empty.
+				if rok {
+					for !ss.At().Iterator().Next() {
+						rok = ss.Next()
+						if !rok {
+							break
+						}
+					}
+				}
+
+				require.Equal(t, eok, rok, "next")
+
+				if !eok {
+					break
+				}
+				sexp := expSs.At()
+				sres := ss.At()
+
+				require.Equal(t, sexp.Labels(), sres.Labels(), "labels")
+
+				smplExp, errExp := expandSeriesIterator(sexp.Iterator())
+				smplRes, errRes := expandSeriesIterator(sres.Iterator())
+
+				require.Equal(t, errExp, errRes, "samples error")
+				require.Equal(t, smplExp, smplRes, "samples")
+			}
+		}
+	}
+
+	return
+}
+
+func boundedSamples(full []sample, mint, maxt int64) []sample {
+	start, end := -1, -1
+	for i, s := range full {
+		if s.t >= mint {
+			start = i
+			break
+		}
+	}
+	if start == -1 {
+		start = len(full)
+	}
+
+	for i, s := range full[start:] {
+		if s.t > maxt {
+			end = start + i
+			break
+		}
+	}
+
+	if end == -1 {
+		end = len(full)
+	}
+
+	return full[start:end]
+}
+
+func matchLSet(m labels.Matcher, ls labels.Labels) bool {
+	for _, l := range ls {
+		if m.Name() == l.Name && m.Matches(l.Value) {
+			return true
+		}
+	}
+
+	return false
+}