test: don't override Fake::HTTP.new (#72)

GitHub: fix GH-70

`Fake::HTTP.new` used `Class.method(:new).unbind.bind(self)` to bypass
`Net::HTTP.new`. It fails with Ruby 4.1 because `Class.method(:new)` is
a singleton method of `Class` now:

```text
TypeError: singleton method called for a different object
```

We don't need to bypass `Net::HTTP.new`. We can use the default
`Net::HTTP#initialize` and set responses by an attribute writer instead.

Reported by Mamoru TASAKA. Thanks!!!

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: kou

test/test_client.rb

@@ -14,17 +14,7 @@ class ClientTest < Test::Unit::TestCase
 
   module Fake
     class HTTP < Net::HTTP
-      class << self
-        def new(*args, &block)
-          Class.method(:new).unbind.bind(self).call(*args, &block)
-        end
-      end
-
-      def initialize responses = {}
-        super("127.0.0.1")
-        @started = false
-        @responses = responses
-      end
+      attr_writer :responses
 
       def started?
         @started
@@ -57,7 +47,7 @@ def initialize(*args)
 
       private
       def net_http host, port, proxy_host, proxy_port
-        HTTP.new
+        HTTP.new("127.0.0.1")
       end
     end
 
@@ -353,7 +343,11 @@ def read filename
 
   def fake_client(responses, uri)
     client_class = Class.new(Fake::Client) {
-      define_method(:net_http) { |*_| Fake::HTTP.new(responses) }
+      define_method(:net_http) do |*_|
+        http = Fake::HTTP.new("127.0.0.1")
+        http.responses = responses
+        http
+      end
     }
     client = client_class.new2(uri)
     client.set_parser(parser)