add tests #4455

	'on':
	push: null
	pull_request: null
	workflow_dispatch: null
	jobs:
	format-checker:
	runs-on: ubuntu-latest
	env:
	# When there is no base commit (e.g., first push to a new branch),
	# GitHub assigns a string of zeros to event.before. It's necessary to
	# handle this separately
	NULL_COMMIT: '0000000000000000000000000000000000000000'
	steps:
	- uses: actions/checkout@v3
	with:
	fetch-depth: 0
	- name: Install Python 3
	uses: actions/setup-python@v4
	with:
	python-version: 3.10.6
	- name: Install dependencies
	run: \|
	python -m pip install --upgrade pip
	pip install -r format_checker/requirements.txt
	# Only run this step if the event is a push and event.before shows
	# that it's the first push to a new branch
	- if: >-
	${{github.event_name == 'push' && github.event.before ==
	env.NULL_COMMIT}}
	name: Run format checker on new branch
	run: >
	python format_checker/main.py ${{github.event.before}}
	${{github.event.commits[0].id}} ${{github.event.after}}
	# Only run this step if the event is a pull request
	- if: ${{github.event_name == 'pull_request'}}
	name: Run format checker on pull request
	run: >
	python format_checker/main.py ${{github.event.pull_request.base.sha}}
	${{github.event.pull_request.head.sha}}
	# Only run this step if the event is a push and it's not the first one
	# to a new branch
	- if: >-
	${{github.event_name == 'push' && github.event.before !=
	env.NULL_COMMIT}}
	name: Run format checker on push
	run: >
	python format_checker/main.py ${{github.event.before}}
	${{github.event.after}}

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