Sample

Assert Rack::Test::UploadedFile defaults content_type to text/plain rather than inferring MIME types from file extensions and default_host defaults to example.org

sha256:a547a5386ea49e912d3240302a7c7194b1828e054d1785eb75c673f73f3711ef

PUBLISHED L3_CONTRACT_PASS MIT-0

Case

Goal: Assert Rack::Test::UploadedFile defaults content_type to text/plain rather than inferring MIME types from file extensions and default_host defaults to example.org HOW
Packages: rack-test 2.2.0 rack 3.2.7
Environment: ruby
Created: 2026-08-16T16:44:42Z

Rack::Test::UploadedFile automatically infers the MIME content type from the file extension when the content_type argument is omitted.

The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.

Rack::Test::UploadedFile.new with an image file path returns 'text/plain' for content_type rather than 'image/png' when the argument is omitted, because UploadedFile defaults content_type to 'text/plain' without inspecting the filename extension.
assert posting an UploadedFile without an explicit content_type sends 'content-type: text/plain' in the multipart body and parses into params with :type 'text/plain'
assert passing an explicit content_type argument overrides the default and preserves 'image/png' in both UploadedFile and multipart params
assert UploadedFile wrapping a StringIO defaults content_type to 'text/plain' when content_type is left unset
assert Rack::Test::Session defaults default_host to 'example.org' rather than 'localhost' when initialized without an explicit host

ruby 3 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · rubygems@1 · 2026-08-16 · ed25519:d91480838ac982c9