chore: Add a test workflow (#679)

* chore: Add a test workflow

* chore: Add pip constraints

* chore: Add dependabot

* chore: Add workflow trigger

* chore: Fix matrix yaml indentation

* chore: Fix file name

* chore: Add poetry cache

* chore: Remove duplicate step

* chore: Move poetry installation step before setup-python

* chore: Use explicit Python version for Poetry venv

* chore: Add lint job

* chore: Use tox environments in matrix

* test: Mark all tests under tests/external*/ as 'external'

* test: Combine coverage

* test: Continue to coverage if external tests fail

* test: Add --parallel flag for coverage

* Make sure tox is installed

* Fix tox env name

* Upload coverage

* Coverage fail under 85%

* Add doctest to matrix

* Add dependabot for GitHub Actions

* skip external tests temporarily

Co-authored-by: Aaron ("AJ") Steers <aj@meltano.com>

.github/dependabot.yml

@@ -0,0 +1,16 @@
+version: 2
+updates:
+  - package-ecosystem: pip
+    directory: "/.github/workflows"
+    schedule:
+      interval: daily
+      time: "12:00"
+      timezone: "UTC"
+    reviewers: [meltano-engineering]
+    labels: [deps]
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly
+    reviewers: [meltano-engineering]
+    labels: [deps]

.github/workflows/constraints.txt

@@ -0,0 +1,3 @@
+pip==22.1.1
+poetry==1.1.13
+virtualenv==20.14.1

.github/workflows/test.yml

@@ -0,0 +1,112 @@
+name: Test
+
+on:
+  pull_request: {}
+  push:
+    branches: [main]
+  workflow_dispatch:
+    inputs: {}
+
+jobs:
+  tests:
+    name: Test on ${{ matrix.python-version }} (${{ matrix.tox-env }}${{ matrix.external && ', external' || '' }}) / ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    continue-on-error: ${{ matrix.external || false }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+        - { tox-env: py, python-version: "3.7", os: "ubuntu-latest" }
+        - { tox-env: py, python-version: "3.8", os: "ubuntu-latest" }
+        - { tox-env: py, python-version: "3.9", os: "ubuntu-latest" }
+        - { tox-env: py, python-version: "3.10", os: "ubuntu-latest" }
+        #TODO: resolve by mapping CI vars to creds: 
+        # https://github.com/meltano/sdk/issues/683
+        # - { tox-env: py, python-version: "3.10", os: "ubuntu-latest", external: true }
+        - { tox-env: doctest, python-version: "3.10", os: "ubuntu-latest" }
+        - { tox-env: lint, python-version: "3.8", os: "ubuntu-latest" }
+
+    steps:
+    - name: Check out the repository
+      uses: actions/checkout@v3.0.2
+
+    - name: Install Poetry
+      env:
+        PIP_CONSTRAINT: .github/workflows/constraints.txt
+      run: |
+        pipx install poetry
+        poetry --version
+
+    - name: Setup Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v3.1.2
+      with:
+        python-version: ${{ matrix.python-version }}
+        architecture: x64
+        cache: 'poetry'
+
+    - name: Upgrade pip
+      env:
+        PIP_CONSTRAINT: .github/workflows/constraints.txt
+      run: |
+        pip install pip
+        pip --version
+
+    - name: Install Dependencies
+      run: |
+        poetry env use "${{ matrix.python-version }}"
+        poetry install
+
+    - name: Run tox
+      run: |
+        poetry run tox -e ${{ matrix.tox-env }} --${{ matrix.external && ' -m "external"' || '' }}${{ matrix.doctest && ' --doctest-modules singer_sdk' }}
+
+    - name: Upload coverage data
+      if: always() && (matrix.tox-env == 'py')
+      uses: actions/upload-artifact@v3.1.0
+      with:
+        name: coverage-data
+        path: ".coverage.*"
+
+  coverage:
+    runs-on: ubuntu-latest
+    needs: tests
+    steps:
+    - name: Check out the repository
+      uses: actions/checkout@v3.0.2
+
+    - name: Install Poetry
+      run: |
+        pipx install --pip-args=--constraint=.github/workflows/constraints.txt poetry
+        poetry --version
+
+    - name: Set up Python
+      uses: actions/setup-python@v3.1.2
+      with:
+        python-version: '3.10'
+        cache: 'poetry'
+
+    - name: Upgrade pip
+      run: |
+        pip install --constraint=.github/workflows/constraints.txt pip
+        pip --version
+
+    - name: Download coverage data
+      uses: actions/download-artifact@v3.0.0
+      with:
+        name: coverage-data
+
+    - name: Install Dependencies
+      run: |
+        poetry env use "3.10"
+        poetry install
+
+    - name: Combine coverage data and display human readable report
+      run: |
+        poetry run tox -e combine_coverage
+
+    - name: Create coverage report
+      run: |
+        poetry run tox -e coverage_xml
+
+    - name: Upload coverage report
+      uses: codecov/codecov-action@v3.1.0