diff --git a/prometheus/promhttp/instrument_client_1_8_test.go b/prometheus/promhttp/instrument_client_1_8_test.go
deleted file mode 100644
index 7e3f522..0000000
--- a/prometheus/promhttp/instrument_client_1_8_test.go
+++ /dev/null
@@ -1,195 +0,0 @@
-// Copyright 2017 The Prometheus Authors
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// +build go1.8
-
-package promhttp
-
-import (
-	"log"
-	"net/http"
-	"testing"
-	"time"
-
-	"github.com/prometheus/client_golang/prometheus"
-)
-
-func TestClientMiddlewareAPI(t *testing.T) {
-	client := http.DefaultClient
-	client.Timeout = 1 * time.Second
-
-	reg := prometheus.NewRegistry()
-
-	inFlightGauge := prometheus.NewGauge(prometheus.GaugeOpts{
-		Name: "client_in_flight_requests",
-		Help: "A gauge of in-flight requests for the wrapped client.",
-	})
-
-	counter := prometheus.NewCounterVec(
-		prometheus.CounterOpts{
-			Name: "client_api_requests_total",
-			Help: "A counter for requests from the wrapped client.",
-		},
-		[]string{"code", "method"},
-	)
-
-	dnsLatencyVec := prometheus.NewHistogramVec(
-		prometheus.HistogramOpts{
-			Name:    "dns_duration_seconds",
-			Help:    "Trace dns latency histogram.",
-			Buckets: []float64{.005, .01, .025, .05},
-		},
-		[]string{"event"},
-	)
-
-	tlsLatencyVec := prometheus.NewHistogramVec(
-		prometheus.HistogramOpts{
-			Name:    "tls_duration_seconds",
-			Help:    "Trace tls latency histogram.",
-			Buckets: []float64{.05, .1, .25, .5},
-		},
-		[]string{"event"},
-	)
-
-	histVec := prometheus.NewHistogramVec(
-		prometheus.HistogramOpts{
-			Name:    "request_duration_seconds",
-			Help:    "A histogram of request latencies.",
-			Buckets: prometheus.DefBuckets,
-		},
-		[]string{"method"},
-	)
-
-	reg.MustRegister(counter, tlsLatencyVec, dnsLatencyVec, histVec, inFlightGauge)
-
-	trace := &InstrumentTrace{
-		DNSStart: func(t float64) {
-			dnsLatencyVec.WithLabelValues("dns_start")
-		},
-		DNSDone: func(t float64) {
-			dnsLatencyVec.WithLabelValues("dns_done")
-		},
-		TLSHandshakeStart: func(t float64) {
-			tlsLatencyVec.WithLabelValues("tls_handshake_start")
-		},
-		TLSHandshakeDone: func(t float64) {
-			tlsLatencyVec.WithLabelValues("tls_handshake_done")
-		},
-	}
-
-	client.Transport = InstrumentRoundTripperInFlight(inFlightGauge,
-		InstrumentRoundTripperCounter(counter,
-			InstrumentRoundTripperTrace(trace,
-				InstrumentRoundTripperDuration(histVec, http.DefaultTransport),
-			),
-		),
-	)
-
-	resp, err := client.Get("http://google.com")
-	if err != nil {
-		t.Fatalf("%v", err)
-	}
-	defer resp.Body.Close()
-}
-
-func ExampleInstrumentRoundTripperDuration() {
-	client := http.DefaultClient
-	client.Timeout = 1 * time.Second
-
-	inFlightGauge := prometheus.NewGauge(prometheus.GaugeOpts{
-		Name: "client_in_flight_requests",
-		Help: "A gauge of in-flight requests for the wrapped client.",
-	})
-
-	counter := prometheus.NewCounterVec(
-		prometheus.CounterOpts{
-			Name: "client_api_requests_total",
-			Help: "A counter for requests from the wrapped client.",
-		},
-		[]string{"code", "method"},
-	)
-
-	// dnsLatencyVec uses custom buckets based on expected dns durations.
-	// It has an instance label "event", which is set in the
-	// DNSStart and DNSDonehook functions defined in the
-	// InstrumentTrace struct below.
-	dnsLatencyVec := prometheus.NewHistogramVec(
-		prometheus.HistogramOpts{
-			Name:    "dns_duration_seconds",
-			Help:    "Trace dns latency histogram.",
-			Buckets: []float64{.005, .01, .025, .05},
-		},
-		[]string{"event"},
-	)
-
-	// tlsLatencyVec uses custom buckets based on expected tls durations.
-	// It has an instance label "event", which is set in the
-	// TLSHandshakeStart and TLSHandshakeDone hook functions defined in the
-	// InstrumentTrace struct below.
-	tlsLatencyVec := prometheus.NewHistogramVec(
-		prometheus.HistogramOpts{
-			Name:    "tls_duration_seconds",
-			Help:    "Trace tls latency histogram.",
-			Buckets: []float64{.05, .1, .25, .5},
-		},
-		[]string{"event"},
-	)
-
-	// histVec has no labels, making it a zero-dimensional ObserverVec.
-	histVec := prometheus.NewHistogramVec(
-		prometheus.HistogramOpts{
-			Name:    "request_duration_seconds",
-			Help:    "A histogram of request latencies.",
-			Buckets: prometheus.DefBuckets,
-		},
-		[]string{},
-	)
-
-	// Register all of the metrics in the standard registry.
-	prometheus.MustRegister(counter, tlsLatencyVec, dnsLatencyVec, histVec, inFlightGauge)
-
-	// Define functions for the available httptrace.ClientTrace hook
-	// functions that we want to instrument.
-	trace := &InstrumentTrace{
-		DNSStart: func(t float64) {
-			dnsLatencyVec.WithLabelValues("dns_start")
-		},
-		DNSDone: func(t float64) {
-			dnsLatencyVec.WithLabelValues("dns_done")
-		},
-		TLSHandshakeStart: func(t float64) {
-			tlsLatencyVec.WithLabelValues("tls_handshake_start")
-		},
-		TLSHandshakeDone: func(t float64) {
-			tlsLatencyVec.WithLabelValues("tls_handshake_done")
-		},
-	}
-
-	// Wrap the default RoundTripper with middleware.
-	roundTripper := InstrumentRoundTripperInFlight(inFlightGauge,
-		InstrumentRoundTripperCounter(counter,
-			InstrumentRoundTripperTrace(trace,
-				InstrumentRoundTripperDuration(histVec, http.DefaultTransport),
-			),
-		),
-	)
-
-	// Set the RoundTripper on our client.
-	client.Transport = roundTripper
-
-	resp, err := client.Get("http://google.com")
-	if err != nil {
-		log.Printf("error: %v", err)
-	}
-	defer resp.Body.Close()
-}