Add dependency caching to builds

.github/workflows/test.yml

@@ -20,23 +20,37 @@ jobs:
       uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
-    - name: Install dependencies
-      run: |
-        python -m pip install --upgrade pip
-        pip install poetry
-        poetry install
-        pip install coveralls==3.2.0
+
+    - name: Install Poetry
+      uses: snok/install-poetry@v1.1.6
+      with:
+        virtualenvs-create: true
+        virtualenvs-in-project: true
+
+    - name: Load cached venv
+      id: cached-poetry-dependencies
+      uses: actions/cache@v2
+      with:
+        path: .venv
+        key: venv-${{ runner.os }}-${{ matrix.python-version }}-${{ hashFiles('**/poetry.lock') }}
+
+    - name: Install library and dependencies
+      run: poetry install --no-interaction
+
     - name: Lint with flake8
       run: |
         # stop the build if there are Python syntax errors or undefined names
         poetry run flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
         # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
         poetry run flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+
     - name: Test with pytest
       run: |
         poetry run pytest --doctest-modules changetext ./tests --cov=.
+
     - name: Upload coverage data to coveralls.io
       run: |
+        pip install coveralls==3.2.0
         coveralls --service=github
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}