CHANGELOG.md in govuk_ab_testing-2.3.0 vs CHANGELOG.md in govuk_ab_testing-2.3.1

@@ -1,4 +1,10 @@
+## 2.3.1
+
+* Fix bug in order to allow us to set multiple headers (i.e. A/B tests) in a
+  test using Capybara. This is important when running multiple A/B tests at
+  once.
+
 ## 2.3.0
 
 * Fix for Rails 5.0.2 - the Active Support acceptance tests used to memoize
   the `@request` and `@response` objects. This worked fine in Rails 4, but
   it looks like Rails 5 now points to a different object at some point during