Lua /etc/resolv.conf parser and some refactoring

rootfs/etc/nginx/lua/test/helpers.lua

@@ -0,0 +1,47 @@
+local _M = {}
+
+local resty_dns_resolver = require("resty.dns.resolver")
+
+local original_resty_dns_resolver_new = resty_dns_resolver.new
+local original_io_open = io.open
+
+function _M.with_resolv_conf(content, func)
+  local new_resolv_conf_f = assert(io.tmpfile())
+  new_resolv_conf_f:write(content)
+  new_resolv_conf_f:seek("set", 0)
+
+  io.open = function(path, mode)
+    if path ~= "/etc/resolv.conf" then
+      error("expected '/etc/resolv.conf' as path but got: " .. tostring(path))
+    end
+    if mode ~= "r" then
+      error("expected 'r' as mode but got: " .. tostring(mode))
+    end
+
+    return new_resolv_conf_f, nil
+  end
+
+  func()
+
+  io.open = original_io_open
+
+  if io.type(new_resolv_conf_f) ~= "closed file" then
+    error("file was left open")
+  end
+end
+
+function _M.mock_resty_dns_new(func)
+  resty_dns_resolver.new = func
+end
+
+function _M.mock_resty_dns_query(response, err)
+  resty_dns_resolver.new = function(self, options)
+    local r = original_resty_dns_resolver_new(self, options)
+    r.query = function(self, name, options, tries)
+      return response, err
+    end
+    return r
+  end
+end
+
+return _M