Fix MockResponse#body when the body is a Proc (#2420)

tavianator · ioquatix · commit 3b8b0d22d68a · 2026-02-12T21:18:41.000+13:00
- Ensure streaming response body is closed by `Rack::MockResponse`. (#2423)
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 All notable changes to this project will be documented in this file. For info on how to format all future additions to this file please reference [Keep A Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## Unreleased
+
+### Fixed
+
+- Fix `Rack::MockResponse#body` when the body is a Proc. ([#2420](https://github.com/rack/rack/pull/2420), [#2423](https://github.com/rack/rack/pull/2423), [@tavianator](https://github.com/tavianator), [@ioquatix])
+
 ## [3.2.4] - 2025-11-03
 
 ### Fixed
diff --git a/lib/rack/mock_response.rb b/lib/rack/mock_response.rb
@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require 'stringio'
 require 'time'
 
 require_relative 'response'
@@ -82,8 +83,16 @@ def body
       #   end
       buffer = @buffered_body = String.new
 
-      @body.each do |chunk|
-        buffer << chunk
+      begin
+        if @body.respond_to?(:each)
+          @body.each do |chunk|
+            buffer << chunk
+          end
+        else
+          @body.call(StringIO.new(buffer))
+        end
+      ensure
+        @body.close if @body.respond_to?(:close)
       end
 
       return buffer
diff --git a/test/spec_mock_response.rb b/test/spec_mock_response.rb
@@ -230,6 +230,42 @@ def close
     headers = res[1]
     refute headers.key?("content-length")
   end
+
+  it "handles Proc bodies" do
+    headers = { "content-type" => "text/event-stream" }
+
+    body = proc do |stream|
+      stream.write("Hello, ")
+      stream.write("world!")
+    end
+
+    response = Rack::MockResponse[200, headers, body]
+
+    response.status.must_equal 200
+    response.headers.must_equal headers
+    response.body.must_equal "Hello, world!"
+  end
+
+  it "closes streaming bodies that respond to close" do
+    closed = false
+
+    body = proc do |stream|
+      stream.write("content")
+    end
+
+    # Add a close method to the proc
+    def body.close
+      @closed = true
+    end
+
+    def body.closed?
+      @closed
+    end
+
+    response = Rack::MockResponse[200, {}, body]
+    response.body.must_equal "content"
+    body.must_be :closed?
+  end
 end
 
 describe Rack::MockResponse, 'headers' do
