diff --git a/cmd/tsdb/main.go b/cmd/tsdb/main.go
index 8c0494510e..d4fdc6251f 100644
--- a/cmd/tsdb/main.go
+++ b/cmd/tsdb/main.go
@@ -107,7 +107,9 @@ func main() {
 		}
 		dumpSamples(db, *dumpMinTime, *dumpMaxTime)
 	}
-	flag.CommandLine.Set("log.level", "debug")
+	if err := flag.CommandLine.Set("log.level", "debug"); err != nil {
+		exitWithError(err)
+	}
 }
 
 type writeBenchmark struct {
diff --git a/compact_test.go b/compact_test.go
index 90819bcf92..2580478569 100644
--- a/compact_test.go
+++ b/compact_test.go
@@ -27,7 +27,6 @@ import (
 	"github.com/go-kit/kit/log"
 	"github.com/pkg/errors"
 	prom_testutil "github.com/prometheus/client_golang/prometheus/testutil"
-	dto "github.com/prometheus/client_model/go"
 	"github.com/prometheus/tsdb/chunks"
 	"github.com/prometheus/tsdb/fileutil"
 	"github.com/prometheus/tsdb/labels"
@@ -744,7 +743,7 @@ func TestCompaction_populateBlock(t *testing.T) {
 		if ok := t.Run(tc.title, func(t *testing.T) {
 			blocks := make([]BlockReader, 0, len(tc.inputSeriesSamples))
 			for _, b := range tc.inputSeriesSamples {
-				ir, cr, mint, maxt := createIdxChkReaders(b)
+				ir, cr, mint, maxt := createIdxChkReaders(t, b)
 				blocks = append(blocks, &mockBReader{ir: ir, cr: cr, mint: mint, maxt: maxt})
 			}
 
@@ -890,16 +889,14 @@ func TestDisableAutoCompactions(t *testing.T) {
 	default:
 	}
 
-	m := &dto.Metric{}
 	for x := 0; x < 10; x++ {
-		db.metrics.compactionsSkipped.Write(m)
-		if *m.Counter.Value > float64(0) {
+		if prom_testutil.ToFloat64(db.metrics.compactionsSkipped) > 0.0 {
 			break
 		}
 		time.Sleep(10 * time.Millisecond)
 	}
 
-	testutil.Assert(t, *m.Counter.Value > float64(0), "No compaction was skipped after the set timeout.")
+	testutil.Assert(t, prom_testutil.ToFloat64(db.metrics.compactionsSkipped) > 0.0, "No compaction was skipped after the set timeout.")
 	testutil.Equals(t, 0, len(db.blocks))
 
 	// Enable the compaction, trigger it and check that the block is persisted.
diff --git a/go.mod b/go.mod
index df0015df3a..02f3cf9e78 100644
--- a/go.mod
+++ b/go.mod
@@ -18,7 +18,7 @@ require (
 	github.com/pkg/errors v0.8.0
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/prometheus/client_golang v0.9.1
-	github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910
+	github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910 // indirect
 	github.com/prometheus/common v0.0.0-20181113130724-41aa239b4cce // indirect
 	github.com/prometheus/procfs v0.0.0-20181005140218-185b4288413d // indirect
 	github.com/stretchr/testify v1.2.2 // indirect
diff --git a/head_test.go b/head_test.go
index 4fbdec03af..9e78b6b624 100644
--- a/head_test.go
+++ b/head_test.go
@@ -859,7 +859,7 @@ func TestGCChunkAccess(t *testing.T) {
 	_, err = cr.Chunk(chunks[1].Ref)
 	testutil.Ok(t, err)
 
-	h.Truncate(1500) // Remove a chunk.
+	testutil.Ok(t, h.Truncate(1500)) // Remove a chunk.
 
 	_, err = cr.Chunk(chunks[0].Ref)
 	testutil.Equals(t, ErrNotFound, err)
@@ -899,7 +899,7 @@ func TestGCSeriesAccess(t *testing.T) {
 	_, err = cr.Chunk(chunks[1].Ref)
 	testutil.Ok(t, err)
 
-	h.Truncate(2000) // Remove the series.
+	testutil.Ok(t, h.Truncate(2000)) // Remove the series.
 
 	testutil.Equals(t, (*memSeries)(nil), h.series.getByID(1))
 
diff --git a/index/index.go b/index/index.go
index 9e5ceccecc..6b333fa584 100644
--- a/index/index.go
+++ b/index/index.go
@@ -53,7 +53,6 @@ const (
 type indexWriterSeries struct {
 	labels labels.Labels
 	chunks []chunks.Meta // series file offset of chunks
-	offset uint32        // index file offset of series reference
 }
 
 type indexWriterSeriesSlice []*indexWriterSeries
diff --git a/index/index_test.go b/index/index_test.go
index b82d07d2a2..43b737c7d1 100644
--- a/index/index_test.go
+++ b/index/index_test.go
@@ -295,7 +295,7 @@ func TestPersistence_index_e2e(t *testing.T) {
 	for i, s := range input {
 		err = iw.AddSeries(uint64(i), s.labels, s.chunks...)
 		testutil.Ok(t, err)
-		mi.AddSeries(uint64(i), s.labels, s.chunks...)
+		testutil.Ok(t, mi.AddSeries(uint64(i), s.labels, s.chunks...))
 
 		for _, l := range s.labels {
 			valset, ok := values[l.Name]
@@ -325,7 +325,7 @@ func TestPersistence_index_e2e(t *testing.T) {
 	}
 	err = iw.WritePostings("", "", newListPostings(all...))
 	testutil.Ok(t, err)
-	mi.WritePostings("", "", newListPostings(all...))
+	testutil.Ok(t, mi.WritePostings("", "", newListPostings(all...)))
 
 	for n, e := range postings.m {
 		for v := range e {
diff --git a/labels/labels.go b/labels/labels.go
index d1ba70b454..35a230f57c 100644
--- a/labels/labels.go
+++ b/labels/labels.go
@@ -204,9 +204,7 @@ func ReadLabels(fn string, n int) ([]Labels, error) {
 		hashes[h] = struct{}{}
 		i++
 	}
-	if err != nil {
-		return nil, err
-	}
+
 	if i != n {
 		return mets, errors.Errorf("requested %d metrics but found %d", n, i)
 	}
diff --git a/querier_test.go b/querier_test.go
index 3b70032829..d190840fd8 100644
--- a/querier_test.go
+++ b/querier_test.go
@@ -194,7 +194,7 @@ type seriesSamples struct {
 
 // Index: labels -> postings -> chunkMetas -> chunkRef
 // ChunkReader: ref -> vals
-func createIdxChkReaders(tc []seriesSamples) (IndexReader, ChunkReader, int64, int64) {
+func createIdxChkReaders(t *testing.T, tc []seriesSamples) (IndexReader, ChunkReader, int64, int64) {
 	sort.Slice(tc, func(i, j int) bool {
 		return labels.Compare(labels.FromMap(tc[i].lset), labels.FromMap(tc[i].lset)) < 0
 	})
@@ -234,7 +234,7 @@ func createIdxChkReaders(tc []seriesSamples) (IndexReader, ChunkReader, int64, i
 		}
 
 		ls := labels.FromMap(s.lset)
-		mi.AddSeries(uint64(i), ls, metas...)
+		testutil.Ok(t, mi.AddSeries(uint64(i), ls, metas...))
 
 		postings.Add(uint64(i), ls)
 
@@ -249,12 +249,12 @@ func createIdxChkReaders(tc []seriesSamples) (IndexReader, ChunkReader, int64, i
 	}
 
 	for l, vs := range lblIdx {
-		mi.WriteLabelIndex([]string{l}, vs.slice())
+		testutil.Ok(t, mi.WriteLabelIndex([]string{l}, vs.slice()))
 	}
 
-	postings.Iter(func(l labels.Label, p index.Postings) error {
+	testutil.Ok(t, postings.Iter(func(l labels.Label, p index.Postings) error {
 		return mi.WritePostings(l.Name, l.Value, p)
-	})
+	}))
 
 	return mi, chkReader, blockMint, blockMaxt
 }
@@ -363,7 +363,7 @@ func TestBlockQuerier(t *testing.T) {
 
 Outer:
 	for _, c := range cases.queries {
-		ir, cr, _, _ := createIdxChkReaders(cases.data)
+		ir, cr, _, _ := createIdxChkReaders(t, cases.data)
 		querier := &blockQuerier{
 			index:      ir,
 			chunks:     cr,
@@ -525,7 +525,7 @@ func TestBlockQuerierDelete(t *testing.T) {
 
 Outer:
 	for _, c := range cases.queries {
-		ir, cr, _, _ := createIdxChkReaders(cases.data)
+		ir, cr, _, _ := createIdxChkReaders(t, cases.data)
 		querier := &blockQuerier{
 			index:      ir,
 			chunks:     cr,
@@ -630,7 +630,7 @@ func TestBaseChunkSeries(t *testing.T) {
 	for _, tc := range cases {
 		mi := newMockIndex()
 		for _, s := range tc.series {
-			mi.AddSeries(s.ref, s.lset, s.chunks...)
+			testutil.Ok(t, mi.AddSeries(s.ref, s.lset, s.chunks...))
 		}
 
 		bcs := &baseChunkSeries{
@@ -1884,7 +1884,7 @@ func TestPostingsForMatchers(t *testing.T) {
 
 		for p.Next() {
 			lbls := labels.Labels{}
-			ir.Series(p.At(), &lbls, &[]chunks.Meta{})
+			testutil.Ok(t, ir.Series(p.At(), &lbls, &[]chunks.Meta{}))
 			if _, ok := exp[lbls.String()]; !ok {
 				t.Errorf("Evaluating %v, unexpected result %s", c.matchers, lbls.String())
 			} else {
diff --git a/repair_test.go b/repair_test.go
index 19b663fea5..15e85ff64a 100644
--- a/repair_test.go
+++ b/repair_test.go
@@ -69,7 +69,7 @@ func TestRepairBadIndexVersion(t *testing.T) {
 	testutil.NotOk(t, err)
 
 	// Touch chunks dir in block.
-	os.MkdirAll(filepath.Join(dbDir, "chunks"), 0777)
+	testutil.Ok(t, os.MkdirAll(filepath.Join(dbDir, "chunks"), 0777))
 	defer func() {
 		testutil.Ok(t, os.RemoveAll(filepath.Join(dbDir, "chunks")))
 	}()
diff --git a/tombstones_test.go b/tombstones_test.go
index 80d5ef2040..d60ef832dd 100644
--- a/tombstones_test.go
+++ b/tombstones_test.go
@@ -139,7 +139,8 @@ func TestMemTombstonesConcurrency(t *testing.T) {
 	}()
 	go func() {
 		for x := 0; x < totalRuns; x++ {
-			tomb.Get(uint64(x))
+			_, err := tomb.Get(uint64(x))
+			testutil.Ok(t, err)
 		}
 		wg.Done()
 	}()
diff --git a/wal_test.go b/wal_test.go
index 7b9f965269..7f07a63b9b 100644
--- a/wal_test.go
+++ b/wal_test.go
@@ -146,9 +146,9 @@ func TestSegmentWAL_Truncate(t *testing.T) {
 	var readSeries []RefSeries
 	r := w.Reader()
 
-	r.Read(func(s []RefSeries) {
+	testutil.Ok(t, r.Read(func(s []RefSeries) {
 		readSeries = append(readSeries, s...)
-	}, nil, nil)
+	}, nil, nil))
 
 	testutil.Equals(t, expected, readSeries)
 }