language: ruby
rvm:
  - 1.9
  - 2.0
  - 2.1
  - 2.2
  - 2.3
  - 2.4
  - 2.5
  - 2.6
  - 2.7
  - ruby-head
  - jruby
  - truffleruby
env:
  - RUBYOPT="--enable-frozen-string-literal"
  - RUBYOPT=""
matrix:
  exclude:
    - rvm: 1.9
      env: RUBYOPT="--enable-frozen-string-literal"
    - rvm: 2.0
      env: RUBYOPT="--enable-frozen-string-literal"
    - rvm: 2.1
      env: RUBYOPT="--enable-frozen-string-literal"
    - rvm: 2.2
      env: RUBYOPT="--enable-frozen-string-literal"
    # bundler did not support this back then
    - rvm: 2.3
      env: RUBYOPT="--enable-frozen-string-literal"