What to do when no display name occurs when unittesting Python + Tkinter on Github Actions Memo

Display settings are required when unittesting Python + Tkinter on Github Actions

After git pushing the code repository developed in Python, unittest is automatically run on Github Actions.

When testing a module that requires screen drawing such as Tkinter on GitActions, it is necessary to set the display in the virtual environment. If this setting is not made, an error will be spit out as no display name.

The following is a memo of how to deal with the error. Before running the unit test, set the display with the following contents.

.github\workflows\test.yml

disp=:99
screen=0
geom=640x480x24
exec Xvfb $disp -screen $screen $geom 2>/tmp/Xvfb.log &
export DISPLAY=:99

The yml file for Github Actions looks like this. It is a rule to keep the yml file in .github \ workflows.

.github\workflows\test.yml

name: Python package

on: [push]

jobs:
  build:

    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version: [3.7]

    steps:
    - uses: actions/checkout@v2
    - name: Set up Python ${{ matrix.python-version }}
      uses: actions/setup-python@v2
      with:
        python-version: ${{ matrix.python-version }}
    #Installation
    - name: Install dependencies
      run: |
        python -m pip install --upgrade pip
        pip install flake8 pytest
        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
    #View python version
    - name: Display Python version
      run: python -c "import sys; print(sys.version)"
    #Run unittest
    - name: Test
      run: |
        disp=:99
        screen=0
        geom=640x480x24
        exec Xvfb $disp -screen $screen $geom 2>/tmp/Xvfb.log &
        export DISPLAY=:99
        python -m unittest discover tests

Reference material

I referred to this article on StackOverflow. _tkinter.TclError: no display name and no $DISPLAY environment variable

Other tips on Github Actions

If you want to skip unittests in Github Actions

test.py

@unittest.skipIf("GITHUB_ACTIONS" in os.environ and os.environ["GITHUB_ACTIONS"] == "true", "Skipping this test on Github Actions")
class TestHoge(unittest.TestCase):
    def setUp(self):
        print("setUp")

    def test_hoge(self):
        print("test_hoge")