new file mode 100644
--- /dev/null
+++ b/proxy_cache_use_stale.t
@@ -0,0 +1,190 @@
+#!/usr/bin/perl
+
+# (C) Sergey Kandaurov
+# (C) Nginx, Inc.
+
+# Tests for http proxy cache, proxy_cache_use_stale.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx qw/ :DEFAULT http_end /;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+my $t = Test::Nginx->new()->has(qw/http proxy cache rewrite limit_req/)
+	->write_file_expand('nginx.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    proxy_cache_path   %%TESTDIR%%/cache  levels=1:2  keys_zone=NAME:1m;
+
+    limit_req_zone  $binary_remote_addr  zone=one:1m  rate=15r/m;
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        location / {
+            proxy_pass    http://127.0.0.1:8081;
+
+            proxy_cache   NAME;
+
+            proxy_cache_key  $uri;
+
+            proxy_cache_revalidate  on;
+
+            proxy_cache_background_update  on;
+
+            add_header X-Cache-Status $upstream_cache_status;
+
+            location /t4.html {
+                proxy_pass    http://127.0.0.1:8081/t.html;
+
+                proxy_cache_revalidate  off;
+            }
+
+            location /t5.html {
+                proxy_pass    http://127.0.0.1:8081/t.html;
+
+                proxy_cache_background_update  off;
+            }
+
+            location /updating/ {
+                proxy_pass    http://127.0.0.1:8081/;
+
+                proxy_cache_use_stale  updating;
+            }
+
+            location /t8.html {
+                proxy_pass    http://127.0.0.1:8081/t.html;
+
+                proxy_cache_valid  1s;
+            }
+        }
+    }
+    server {
+        listen       127.0.0.1:8081;
+        server_name  localhost;
+
+        add_header Cache-Control $http_x_cache_control;
+
+        if ($arg_e) {
+            return 500;
+        }
+
+        location / { }
+
+        location /t6.html {
+            limit_req zone=one burst=2;
+        }
+    }
+}
+
+EOF
+
+$t->write_file('t.html', 'SEE-THIS');
+$t->write_file('tt.html', 'SEE-THIS');
+$t->write_file('t2.html', 'SEE-THIS');
+$t->write_file('t3.html', 'SEE-THIS');
+$t->write_file('t6.html', 'SEE-THIS');
+
+$t->try_run('no proxy_cache_background_update')->plan(25);
+
+###############################################################################
+
+like(get('/t.html', 'max-age=1, stale-if-error=5'), qr/MISS/, 'stale-if-error');
+like(http_get('/t.html?e=1'), qr/HIT/, 's-i-e - cached');
+
+like(get('/t2.html', 'max-age=1, stale-while-revalidate=10'), qr/MISS/,
+	'stale-while-revalidate');
+like(http_get('/t2.html'), qr/HIT/, 's-w-r - cached');
+
+get('/tt.html', 'max-age=1, stale-if-error=2');
+get('/t3.html', 'max-age=1, stale-while-revalidate=2');
+get('/t4.html', 'max-age=1, stale-while-revalidate=2');
+get('/t5.html', 'max-age=1, stale-while-revalidate=2');
+get('/t6.html', 'max-age=1, stale-while-revalidate=2');
+get('/updating/t.html', 'max-age=1');
+get('/updating/t2.html', 'max-age=1, stale-while-revalidate=2');
+get('/t8.html', 'stale-while-revalidate=10');
+
+sleep 2;
+
+like(http_get('/t.html?e=1'), qr/STALE/, 's-i-e - stale');
+like(http_get('/tt.html?e=1'), qr/STALE/, 's-i-e - stale 2');
+like(http_get('/t.html'), qr/REVALIDATED/, 's-i-e - revalidated');
+
+like(http_get('/t2.html?e=1'), qr/STALE/, 's-w-r - revalidate error');
+like(http_get('/t2.html'), qr/STALE/, 's-w-r - stale while revalidate');
+like(http_get('/t2.html'), qr/HIT/, 's-w-r - revalidated');
+
+like(get('/t4.html', 'max-age=1, stale-while-revalidate=2'), qr/STALE/,
+	's-w-r - unconditional revalidate');
+like(http_get('/t4.html'), qr/HIT/, 's-w-r - unconditional revalidated');
+
+like(http_get('/t5.html?e=1'), qr/STALE/,
+	's-w-r - foreground revalidate error');
+like(http_get('/t5.html'), qr/REVALIDATED/, 's-w-r - foreground revalidated');
+
+# UPDATING while s–w-r
+
+$t->write_file('t6.html', 'SEE-THAT');
+
+my $s = get('/t6.html', 'max-age=1, stale-while-revalidate=2', start => 1);
+like(http_get('/t6.html'), qr/UPDATING.*SEE-THIS/s, 's-w-r - updating');
+like(http_end($s), qr/STALE.*SEE-THIS/s, 's-w-r - updating stale');
+like(http_get('/t6.html'), qr/HIT.*SEE-THAT/s, 's-w-r - updating revalidated');
+
+# stale-while-revalidate with proxy_cache_use_stale updating
+
+like(http_get('/updating/t.html'), qr/STALE/,
+	's-w-r - use_stale updating stale');
+like(http_get('/updating/t.html'), qr/HIT/,
+	's-w-r - use_stale updating revalidated');
+
+# stale-while-revalidate with proxy_cache_valid
+
+like(http_get('/t8.html'), qr/STALE/, 's-w-r - proxy_cache_valid revalidate');
+like(http_get('/t8.html'), qr/HIT/, 's-w-r - proxy_cache_valid revalidated');
+
+sleep 2;
+
+like(http_get('/t2.html?e=1'), qr/STALE/, 's-w-r - stale after revalidate');
+like(http_get('/t3.html?e=1'), qr/ 500 /, 's-w-r - ceased');
+like(http_get('/tt.html?e=1'), qr/ 500 /, 's-i-e - ceased');
+like(http_get('/updating/t2.html'), qr/STALE/,
+	's-w-r - overriden with use_stale updating');
+
+###############################################################################
+
+sub get {
+	my ($url, $extra, %extra) = @_;
+	return http(<<EOF, %extra);
+GET $url HTTP/1.1
+Host: localhost
+Connection: close
+X-Cache-Control: $extra
+
+EOF
+}
+
+###############################################################################