test: cover WidgetsController, show and ResponderTest

test/test_response.rb

@@ -29,4 +29,48 @@ class ResponseTest < Minitest::Test
     response.set_cookie('b', '2')
     assert_equal 2, response.headers['Set-Cookie'].split("\n").size
   end
+
+  def test_stream_marks_the_response_as_streaming
+    response = Prism::Response.new
+    refute response.streaming?
+    response.stream { |out| out.write('x') }
+    assert response.streaming?
+  end
+
+  def test_stream_body_is_a_streaming_body_not_wrapped_in_an_array
+    response = Prism::Response.new
+    response.stream { |out| out.write('x') }
+    _status, _headers, body = response.finish
+    assert_instance_of Prism::StreamingBody, body
+  end
+
+  def test_streamed_chunks_are_produced_in_write_order
+    response = Prism::Response.new
+    response.stream do |out|
+      out.write('one')
+      out.write('two')
+    end
+    _status, _headers, body = response.finish
+
+    collected = []
+    body.each { |chunk| collected << chunk }
+    assert_equal %w[one two], collected
+  end
+
+  # Regression: `body = value` used to run every assignment through
+  # Kernel#Array, which - given an object with neither #to_ary nor #to_a,
+  # like StreamingBody - wraps it as a one-element Array containing the
+  # streaming object itself instead of leaving it alone, breaking the
+  # #each-based chunking contract Server#write_response relies on.
+  def test_assigning_a_streaming_body_directly_is_not_wrapped_in_an_array
+    response = Prism::Response.new
+    response.body = Prism::StreamingBody.new { |out| out.write('x') }
+    assert_instance_of Prism::StreamingBody, response.body
+  end
+
+  def test_assigning_an_ordinary_string_is_still_wrapped_in_an_array
+    response = Prism::Response.new
+    response.body = 'plain'
+    assert_equal ['plain'], response.body
+  end
 end