fix output buffer corner-case for static files

The write buffer may block on a single write and immediately
become unblocked afterwards.  We need to account for this odd
corner case when serving static files; because clients can
trigger strange corner cases like this.

1 files changed, 7 insertions, 0 deletions

diff --git a/test/server_helper.rb b/test/server_helper.rb
index aeb0dc9..73d3ec8 100644
--- a/test/server_helper.rb
+++ b/test/server_helper.rb
@@ -79,3 +79,10 @@ module ServerHelper
     end
   end
 end
+
+module TrywriteBlocked
+  def kgio_trywrite(*args)
+    return :wait_writable if $_tw_block_on.include?($_tw_blocked += 1)
+    super
+  end
+end