Trick rspec-rails' sub-builds into using 4.0.0.pre

     ============= Starting rspec-rails specs ===============
    Running specs for rspec-rails
    ~/work/rspec-mocks/rspec-rails ~/work/rspec-mocks/rspec-mocks
    Fetching gem metadata from https://rubygems.org/.........
    Fetching gem metadata from https://rubygems.org/.
    Resolving dependencies...
    Bundler could not find compatible versions for gem "rspec-core":
      In Gemfile:
        rspec-core

        rspec-rails was resolved to 4.1.0.pre, which depends on
          rspec-core (= 3.11.0.pre)

    Could not find gem 'rspec-core (= 3.11.0.pre)', which is required by gem
    'rspec-rails', in any of the relevant sources:
      source at `/home/runner/work/rspec-mocks/rspec-core`

Author: pirj

.github/workflows/ci.yml

@@ -11,6 +11,8 @@ on:
   pull_request:
     branches:
       - '*'
+env:
+  RSPEC_CI: true
 jobs:
   test:
     name: Ruby ${{ matrix.ruby }}