Tests optional interfaces in TestResponseWriterTypes

This change tests the functionality of of the http optional interfaces
http.CloseNotifier, http.Hijacker and http.Pusher.

TestResponseWriterTypes already tests to ensure the correct combination
of optional interfaces is produced, this test ensures they are correctly
invoked.

gzip_test.go

@@ -1,10 +1,12 @@
 package gziphandler
 
 import (
+	"bufio"
 	"bytes"
 	"compress/gzip"
 	"io"
 	"io/ioutil"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"strconv"
@@ -330,13 +332,62 @@ func TestInferContentTypeUncompressed(t *testing.T) {
 	assert.Equal(t, "text/html; charset=utf-8", res1.Header.Get("Content-Type"))
 }
 
+type httpCloseNotifierFunc func() <-chan bool
+
+func (fn httpCloseNotifierFunc) CloseNotify() <-chan bool { return fn() }
+
+type httpHijackerFunc func() (net.Conn, *bufio.ReadWriter, error)
+
+func (fn httpHijackerFunc) Hijack() (net.Conn, *bufio.ReadWriter, error) { return fn() }
+
+type httpPusherFunc func(target string, opts *http.PushOptions) error
+
+func (fn httpPusherFunc) Push(target string, opts *http.PushOptions) error { return fn(target, opts) }
+
 func TestResponseWriterTypes(t *testing.T) {
-	var cok, hok, pok bool
+	var closeNotified bool
+	closeNotifier := func() http.CloseNotifier {
+		closeNotified = false
+		return httpCloseNotifierFunc(func() <-chan bool {
+			closeNotified = true
+			return nil
+		})
+	}
 
+	var hijacked bool
+	hijacker := func() http.Hijacker {
+		hijacked = false
+		return httpHijackerFunc(func() (net.Conn, *bufio.ReadWriter, error) {
+			hijacked = true
+			return nil, nil, nil
+		})
+	}
+
+	var pushed bool
+	pusher := func() http.Pusher {
+		pushed = false
+		return httpPusherFunc(func(string, *http.PushOptions) error {
+			pushed = true
+			return nil
+		})
+	}
+
+	var cok, hok, pok bool
 	handler := Gzip(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		_, cok = w.(http.CloseNotifier)
-		_, hok = w.(http.Hijacker)
-		_, pok = w.(http.Pusher)
+		var c http.CloseNotifier
+		if c, cok = w.(http.CloseNotifier); cok {
+			c.CloseNotify()
+		}
+
+		var h http.Hijacker
+		if h, hok = w.(http.Hijacker); hok {
+			h.Hijack()
+		}
+
+		var p http.Pusher
+		if p, pok = w.(http.Pusher); pok {
+			p.Push("", nil)
+		}
 	}))
 
 	req1 := httptest.NewRequest(http.MethodGet, "/whatever", nil)
@@ -350,34 +401,41 @@ func TestResponseWriterTypes(t *testing.T) {
 	handler.ServeHTTP(struct {
 		http.ResponseWriter
 		http.CloseNotifier
-	}{resp1, nil}, req1)
+	}{resp1, closeNotifier()}, req1)
 	assert.True(t, cok && !hok && !pok, "expected CloseNotifier")
+	assert.True(t, closeNotified, "CloseNotify did not call underlying http.CloseNotifier")
 
 	handler.ServeHTTP(struct {
 		http.ResponseWriter
 		http.Hijacker
-	}{resp1, nil}, req1)
+	}{resp1, hijacker()}, req1)
 	assert.True(t, !cok && hok && !pok, "expected Hijacker")
+	assert.True(t, hijacked, "Hijack did not call underlying http.Hijacker")
 
 	handler.ServeHTTP(struct {
 		http.ResponseWriter
 		http.Pusher
-	}{resp1, nil}, req1)
+	}{resp1, pusher()}, req1)
 	assert.True(t, !cok && !hok && pok, "expected Pusher")
+	assert.True(t, pushed, "Push did not call underlying http.Pusher")
 
 	handler.ServeHTTP(struct {
 		http.ResponseWriter
 		http.CloseNotifier
 		http.Hijacker
-	}{resp1, nil, nil}, req1)
+	}{resp1, closeNotifier(), hijacker()}, req1)
 	assert.True(t, cok && hok && !pok, "expected CloseNotifier and Hijacker")
+	assert.True(t, closeNotified, "CloseNotify did not call underlying http.CloseNotifier")
+	assert.True(t, hijacked, "Hijack did not call underlying http.Hijacker")
 
 	handler.ServeHTTP(struct {
 		http.ResponseWriter
 		http.CloseNotifier
 		http.Pusher
-	}{resp1, nil, nil}, req1)
+	}{resp1, closeNotifier(), pusher()}, req1)
 	assert.True(t, cok && !hok && pok, "expected CloseNotifier and Pusher")
+	assert.True(t, closeNotified, "CloseNotify did not call underlying http.CloseNotifier")
+	assert.True(t, pushed, "Push did not call underlying http.Pusher")
 }
 
 func TestContentTypes(t *testing.T) {