3.1.2

What's Changed

• MNT Add behat tests to prove gridfield filter is open by @GuySartorelli in #2032
• FIX Use application/json for Content-Type by @emteknetnz in #2031
• MNT Add unit test for batch action Content-Type by @emteknetnz in #2036
• FIX Ensure arg is integer like by @emteknetnz in #2033
• MNT Update namespace in unit-test by @emteknetnz in #2040

Full Changelog: 3.1.1...3.1.2