diff --git a/integration_test.go b/integration_test.go
index e6823b8..eeaf662 100644
--- a/integration_test.go
+++ b/integration_test.go
@@ -23,7 +23,6 @@ import (
 	"github.com/aws/aws-sdk-go-v2/service/s3"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/testutil"
-	"golang.org/x/sync/singleflight"
 )
 
 const containerName string = "ctile_integration_test_minio"
@@ -144,7 +143,7 @@ func TestIntegration(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	ctile := makeTCH(server.URL, s3Service)
+	ctile := makeTCH(t, server.URL, s3Service)
 
 	// Invalid URL; should 404 passed through to backend and 400
 	resp := getResp(ctile, "/foo")
@@ -277,7 +276,7 @@ func TestIntegration(t *testing.T) {
 	}))
 	defer server.Close()
 
-	erroringCTile := makeTCH(errorCTLog.URL, s3Service)
+	erroringCTile := makeTCH(t, errorCTLog.URL, s3Service)
 	resp = getResp(erroringCTile, "/ct/v1/get-entries?start=0&end=1")
 	if resp.StatusCode != 500 {
 		t.Errorf("expected 500 got %d", resp.StatusCode)
@@ -285,7 +284,7 @@ func TestIntegration(t *testing.T) {
 	expectAndResetMetric(t, erroringCTile.requestsMetric, 1, "error", "ct_log_get")
 }
 
-func getResp(ctile tileCachingHandler, url string) *http.Response {
+func getResp(ctile *tileCachingHandler, url string) *http.Response {
 	req := httptest.NewRequest("GET", url, nil)
 	w := httptest.NewRecorder()
 
@@ -294,7 +293,7 @@ func getResp(ctile tileCachingHandler, url string) *http.Response {
 	return w.Result()
 }
 
-func getAndParseResp(t *testing.T, ctile tileCachingHandler, url string) (entries, http.Header, error) {
+func getAndParseResp(t *testing.T, ctile *tileCachingHandler, url string) (entries, http.Header, error) {
 	t.Helper()
 	resp := getResp(ctile, url)
 	body, _ := io.ReadAll(resp.Body)
@@ -321,21 +320,10 @@ func expectAndResetMetric(t *testing.T, metric *prometheus.CounterVec, expected
 	metric.Reset()
 }
 
-func makeTCH(url string, s3Service *s3.Client) tileCachingHandler {
-	return tileCachingHandler{
-		logURL:   url,
-		tileSize: 3,
-
-		s3Service: s3Service,
-		s3Prefix:  "test",
-		s3Bucket:  "bucket",
-
-		cacheGroup: &singleflight.Group{},
-
-		fullRequestTimeout: 10 * time.Second,
-
-		requestsMetric:     prometheus.NewCounterVec(prometheus.CounterOpts{Help: "foo", Name: "ctile_requests"}, []string{"result", "source"}),
-		partialTiles:       prometheus.NewCounter(prometheus.CounterOpts{Name: "ctile_partial_tiles"}),
-		singleFlightShared: prometheus.NewCounter(prometheus.CounterOpts{Name: "ctile_singleflight_shared"}),
+func makeTCH(t *testing.T, url string, s3Service *s3.Client) *tileCachingHandler {
+	tch, err := newTileCachingHandler(url, 3, s3Service, "test", "bucket", 10*time.Second, prometheus.NewRegistry())
+	if err != nil {
+		t.Fatal(err)
 	}
+	return tch
 }
diff --git a/main.go b/main.go
index 9deece0..021f722 100644
--- a/main.go
+++ b/main.go
@@ -294,6 +294,70 @@ type tileCachingHandler struct {
 	fullRequestTimeout time.Duration
 }
 
+func newTileCachingHandler(
+	logURL string,
+	tileSize int,
+	s3Service *s3.Client,
+	s3Prefix string,
+	s3Bucket string,
+	fullRequestTimeout time.Duration,
+	promRegisterer prometheus.Registerer,
+) (*tileCachingHandler, error) {
+	if logURL == "" {
+		return nil, errors.New("logURL must not be empty")
+	}
+	if tileSize == 0 {
+		return nil, errors.New("tileSize must not be zero")
+	}
+	if s3Service == nil {
+		return nil, errors.New("s3Service must not be nil")
+	}
+	if s3Prefix == "" {
+		return nil, errors.New("s3Prefix must not be empty")
+	}
+	if s3Bucket == "" {
+		return nil, errors.New("s3Bucket must not be empty")
+	}
+	if fullRequestTimeout == 0 {
+		return nil, errors.New("fullRequestTimeout must not be zero")
+	}
+	requestsMetric := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "ctile_requests",
+			Help: "total number of requests, by result and source",
+		},
+		[]string{"result", "source"},
+	)
+	promRegisterer.MustRegister(requestsMetric)
+
+	partialTiles := prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Name: "ctile_partial_tiles",
+			Help: "number of requests not cached due to partial tile returned from CT log",
+		})
+	promRegisterer.MustRegister(partialTiles)
+
+	singleFlightShared := prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Name: "ctile_single_flight_shared",
+			Help: "number of inbound requests coalesced into a single set of backend requests",
+		})
+	promRegisterer.MustRegister(singleFlightShared)
+
+	return &tileCachingHandler{
+		logURL:             logURL,
+		tileSize:           tileSize,
+		s3Service:          s3Service,
+		s3Prefix:           s3Prefix,
+		s3Bucket:           s3Bucket,
+		cacheGroup:         &singleflight.Group{},
+		requestsMetric:     requestsMetric,
+		partialTiles:       partialTiles,
+		singleFlightShared: singleFlightShared,
+		fullRequestTimeout: fullRequestTimeout,
+	}, nil
+}
+
 func (tch *tileCachingHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// For non-get-entries requests, pass them along to the backend
 	if !strings.HasSuffix(r.URL.Path, "/ct/v1/get-entries") {
@@ -527,39 +591,9 @@ func main() {
 
 	promRegistry := newStatsRegistry(*metricsAddress)
 
-	requestsMetric := prometheus.NewCounterVec(
-		prometheus.CounterOpts{
-			Name: "ctile_requests",
-			Help: "total number of requests, by result and source",
-		},
-		[]string{"result", "source"},
-	)
-	promRegistry.MustRegister(requestsMetric)
-
-	partialTiles := prometheus.NewCounter(
-		prometheus.CounterOpts{
-			Name: "ctile_partial_tiles",
-			Help: "number of requests not cached due to partial tile returned from CT log",
-		})
-	promRegistry.MustRegister(partialTiles)
-
-	singleFlightShared := prometheus.NewCounter(
-		prometheus.CounterOpts{
-			Name: "ctile_single_flight_shared",
-			Help: "number of inbound requests coalesced into a single set of backend requests",
-		})
-	promRegistry.MustRegister(singleFlightShared)
-
-	handler := &tileCachingHandler{
-		logURL:             *logURL,
-		tileSize:           *tileSize,
-		s3Service:          svc,
-		s3Prefix:           *s3prefix,
-		s3Bucket:           *s3bucket,
-		cacheGroup:         &singleflight.Group{},
-		requestsMetric:     requestsMetric,
-		partialTiles:       partialTiles,
-		singleFlightShared: singleFlightShared,
+	handler, err := newTileCachingHandler(*logURL, *tileSize, svc, *s3prefix, *s3bucket, *fullRequestTimeout, promRegistry)
+	if err != nil {
+		log.Fatal(err)
 	}
 
 	srv := http.Server{