ci: test on Linux, Windows and macOS with a coverage gate and lint job

.github/workflows/test.yml

@@ -11,9 +11,12 @@ on:
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    name: py${{ matrix.python-version }} on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
         python-version: ["3.10", "3.11", "3.12"]
 
     steps:
@@ -23,14 +26,8 @@ jobs:
         uses: actions/setup-python@v7
         with:
           python-version: ${{ matrix.python-version }}
-
-      - name: Cache pip dependencies
-        uses: actions/cache@v6
-        with:
-          path: ~/.cache/pip
-          key: ${{ runner.os }}-pip-${{ matrix.python-version }}-${{ hashFiles('requirements-dev.txt') }}
-          restore-keys: |
-            ${{ runner.os }}-pip-${{ matrix.python-version }}-
+          cache: pip
+          cache-dependency-path: requirements-dev.txt
 
       - name: Install dependencies
         run: |
@@ -38,9 +35,45 @@ jobs:
           pip install -r requirements-dev.txt
 
       - name: Run tests
-        run: python -m unittest discover tests/ -v
+        run: python -m unittest discover -s tests -v
+
+  coverage:
+    name: coverage gate (85%)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+
+      - uses: actions/setup-python@v7
+        with:
+          python-version: "3.12"
+          cache: pip
+          cache-dependency-path: requirements-dev.txt
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r requirements-dev.txt
+
+      - name: Measure coverage
+        run: |
+          python -m coverage run -m unittest discover -s tests
+          python -m coverage combine
+          python -m coverage report --fail-under=85
+
+  lint:
+    name: black and flake8
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - uses: actions/setup-python@v7
+        with:
+          python-version: "3.12"
+      - run: pip install black flake8
+      - run: black --check .
+      - run: flake8 .
 
   js-test:
+    name: frontend modules
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v7