Update test action to use https://github.com/snok/install-poetry

.github/workflows/tests.yml

@@ -1,34 +1,33 @@
 name: Tests
 
-on: [push, pull_request]
-
-env:
-  POETRY_VIRTUALENVS_IN_PROJECT: "true"
+on: [ push, pull_request ]
 
 jobs:
   run-tests:
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: true
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: [ 3.6, 3.7, 3.8, 3.9 ]
     steps:
       - uses: actions/checkout@v2
-      - name: Set up Python 3.6
+      - name: Set up Python
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install Poetry
-        run: |
-          curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python
-          echo "::add-path::$HOME/.poetry/bin"
-          source $HOME/.poetry/env
-          poetry --version
-      - name: Cache dependencies
+        uses: snok/[email protected]
+        with:
+          virtualenvs-in-project: true
+        run: poetry --version
+      - name: Load cached venv
+        id: cached-poetry-dependencies
         uses: actions/cache@v2
         with:
           path: .venv
-          key: ${{ hashFiles('poetry.lock') }}
+          key: venv-${{ runner.os }}-${{ hashFiles('**/poetry.lock') }}
       - name: Install dependencies
         run: poetry install --no-root
+        if: steps.cached-poetry-dependencies.outputs.cache-hit != 'true'
       - name: Test with pytest
         run: poetry run pytest