Fix flaky TestAccessLogOnFailedRequest (#2573)

Fixes #2571

Signed-off-by: Alexander Yastrebov <alexander.yastrebov@zalando.de>

proxy/proxy_test.go

@@ -2069,14 +2069,12 @@ func TestEnableAccessLogWithFilter(t *testing.T) {
 }
 
 func TestAccessLogOnFailedRequest(t *testing.T) {
-	buf := NewLockedBuffer()
-	logging.Init(logging.Options{
-		AccessLogOutput: buf})
+	testLog := NewTestLog()
+	defer testLog.Close()
 
-	s := httptest.NewServer(http.HandlerFunc(func(http.ResponseWriter, *http.Request) {}))
-	s.Close()
+	logging.Init(logging.Options{AccessLogOutput: testLog})
 
-	p, err := newTestProxy(fmt.Sprintf(`* -> "%s"`, s.URL), 0)
+	p, err := newTestProxy(`* -> "http://bad-gateway.test"`, FlagsNone)
 	if err != nil {
 		t.Fatalf("Failed to create test proxy: %v", err)
 		return
@@ -2086,31 +2084,21 @@ func TestAccessLogOnFailedRequest(t *testing.T) {
 	ps := httptest.NewServer(p.proxy)
 	defer ps.Close()
 
-	rsp, err := http.Get(ps.URL)
+	rsp, err := ps.Client().Get(ps.URL)
 	if err != nil {
 		t.Fatalf("Failed to GET: %v", err)
 		return
 	}
-
 	defer rsp.Body.Close()
 
 	if rsp.StatusCode != http.StatusBadGateway {
 		t.Errorf("failed to return 502 Bad Gateway on failing backend connection: %d", rsp.StatusCode)
 	}
 
-	time.Sleep(time.Millisecond)
-	output := buf.String()
-
-	proxyURL, err := url.Parse(ps.URL)
-	if err != nil {
-		t.Fatalf("Failed to parse url: %v", err)
-		return
-	}
-
-	expected := fmt.Sprintf(`"GET / HTTP/1.1" %d %d "-" "Go-http-client/1.1"`, http.StatusBadGateway, len(http.StatusText(http.StatusBadGateway))+1)
-	if !strings.Contains(output, expected) || !strings.Contains(output, proxyURL.Host) {
-		t.Errorf("Failed to get accesslog '%v' '%v'", output, expected)
-		t.Logf("%s", cmp.Diff(output, expected))
+	const expected = `"GET / HTTP/1.1" 502 12 "-" "Go-http-client/1.1"`
+	if err = testLog.WaitFor(expected, 100*time.Millisecond); err != nil {
+		t.Errorf("Failed to get accesslog %v: %v", expected, err)
+		t.Logf("%s", cmp.Diff(testLog.String(), expected))
 	}
 }