.travis.yml

language: python            # this works for Linux but is an error on macOS or Windows
matrix:
  include:
    - name: "Python 3.7.1 on Xenial Linux"
      python: 3.7           # this works for Linux but is ignored on macOS or Windows
    - name: "Python 3.5 on Xenial Linux"
      python: 3.5           # this works for Linux but is ignored on macOS or Windows
    - name: "Python 3.6 on Xenial Linux"
      python: 3.6           # this works for Linux but is ignored on macOS or Windows
    - name: "Python 3.7.4 on macOS"
      os: osx
      osx_image: xcode11    # Python 3.7.4 running on macOS 10.14.4
      language: shell       # 'language: python' is an error on Travis CI macOS
      #    - name: "Python 3.7.4 on Windows"
      #      os: windows           # Windows 10.0.17134 N/A Build 17134
      #      arch: x64
      #      language: shell       # 'language: python' is an error on Travis CI Windows
      #      before_install:
      #        - choco install python
      #        - python -m pip install --upgrade pip
      #      env: PATH=/c/Python37:/c/Python37/Scripts:$PATH
# install: pip3 install --upgrade pip  # all three OSes agree about 'pip3'
# 'python' points to Python 2.7 on macOS but points to Python 3.7 on Linux and Windows
#" 'python3' is a 'command not found' error on Windows but 'py' works on Windows only
install: python3 setup.py install || python setup.py install
script: python3 setup.py test || python setup.py test