new file mode 100644
--- /dev/null
+++ b/proxy_cookie_flags.t
@@ -0,0 +1,124 @@
+#!/usr/bin/perl
+
+# (C) Sergey Kandaurov
+# (C) Nginx, Inc.
+
+# Tests for the proxy_cookie_flags directive.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+my $t = Test::Nginx->new()->has(qw/http proxy rewrite/);
+
+$t->write_file_expand('nginx.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        location / {
+            proxy_pass http://127.0.0.1:8081;
+
+            proxy_cookie_flags a secure httponly samesite=none;
+            proxy_cookie_flags b secure httponly samesite=lax;
+            proxy_cookie_flags c secure httponly samesite=strict;
+            proxy_cookie_flags d nosecure nohttponly nosamesite;
+
+            proxy_cookie_flags $arg_complex secure;
+            proxy_cookie_flags ~BAR httponly;
+
+            location /off/ {
+                proxy_pass http://127.0.0.1:8081;
+                proxy_cookie_flags off;
+            }
+        }
+    }
+
+    server {
+        listen       127.0.0.1:8081;
+        server_name  localhost;
+
+        location / {
+            set $c "$arg_v$arg_complex=path=domain=; Domain=example.org$arg_f";
+            add_header Set-Cookie $c;
+            return 200 OK;
+        }
+    }
+}
+
+EOF
+
+$t->try_run('no proxy_cookie_flags')->plan(11);
+
+###############################################################################
+
+is(http_get_set_cookie('/?v=a'),
+	'a=path=domain=; Domain=example.org; Secure; HttpOnly; SameSite=None',
+	'flags set all');
+is(http_get_set_cookie('/?v=b'),
+	'b=path=domain=; Domain=example.org; Secure; HttpOnly; SameSite=Lax',
+	'flags set lax');
+is(http_get_set_cookie('/?v=c'),
+	'c=path=domain=; Domain=example.org; Secure; HttpOnly; SameSite=Strict',
+	'flags set strict');
+
+# edit already set flags
+
+is(http_get_set_cookie('/?v=a&f=;Secure;HttpOnly;SameSite=Lax'),
+	'a=path=domain=; Domain=example.org; Secure; HttpOnly; SameSite=None',
+	'flags reset all');
+is(http_get_set_cookie('/?v=b&f=;Secure;HttpOnly;SameSite=None'),
+	'b=path=domain=; Domain=example.org; Secure; HttpOnly; SameSite=Lax',
+	'flags reset lax');
+is(http_get_set_cookie('/?v=c&f=;Secure;HttpOnly;SameSite=None'),
+	'c=path=domain=; Domain=example.org; Secure; HttpOnly; SameSite=Strict',
+	'flags reset strict');
+
+is(http_get_set_cookie('/?v=d&f=;secure;httponly;samesite=lax'),
+	'd=path=domain=; Domain=example.org',
+	'flags remove');
+
+is(http_get_set_cookie('/?v=nx&f=;samesite=none'),
+	'nx=path=domain=; Domain=example.org;samesite=none', 'flags no match');
+
+is(http_get_set_cookie('/?complex=v'),
+	'v=path=domain=; Domain=example.org; Secure', 'flags variable');
+is(http_get_set_cookie('/?v=foobarbaz'),
+	'foobarbaz=path=domain=; Domain=example.org; HttpOnly', 'flags regex');
+
+is(http_get_set_cookie('/off/?v=a'), 'a=path=domain=; Domain=example.org',
+	'flags off');
+
+###############################################################################
+
+sub http_get_set_cookie {
+	my ($uri) = @_;
+	http_get($uri) =~ /^Set-Cookie:\s(.+?)\x0d?$/mi;
+	return $1;
+}
+
+###############################################################################