maint(testing): run tests in stages on actions

.github/workflows/runtests.yml

@@ -13,26 +13,73 @@ jobs:
   # -------------------- Code quality ------------------------------ #
 
   code-quality:
+
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.9
       - run: python -m pip install --upgrade pip
       - run: pip install mpmath flake8
       - run: bin/test quality
       - run: flake8 sympy
 
-  # -------------------- Doctests ---------------------------------- #
+  # -------------------- Doctests latest Python -------------------- #
 
-  doctests:
+  doctests-latest:
+    needs: code-quality
+
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+      - run: python -m pip install --upgrade pip
+      - run: pip install mpmath
+      - run: bin/doctest --force-colors
+      - run: examples/all.py -q
+
+  # -------------------- Test split 1/2 latest Python -------------- #
+
+  tests1-latest:
     needs: code-quality
 
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+      - run: python -m pip install --upgrade pip
+      - run: pip install mpmath
+      - run: bin/test --force-colors --split=1/2
+
+  # -------------------- Test split 2/2 latest Python -------------- #
+
+  tests2-latest:
+    needs: code-quality
+
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+      - run: python -m pip install --upgrade pip
+      - run: pip install mpmath
+      - run: bin/test --force-colors --split=2/2
+
+  # -------------------- Doctests older Python --------------------- #
+
+  doctests:
+    needs: [doctests-latest, tests1-latest, tests2-latest]
+
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: [3.6, 3.7, 3.8]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
@@ -43,15 +90,15 @@ jobs:
       - run: bin/doctest --force-colors
       - run: examples/all.py -q
 
-  # -------------------- Test split 1/2 ---------------------------- #
+  # -------------------- Test split 1/2 older Python --------------- #
 
   tests1:
-    needs: code-quality
+    needs: [doctests-latest, tests1-latest, tests2-latest]
 
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: [3.6, 3.7, 3.8]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
@@ -61,15 +108,15 @@ jobs:
       - run: pip install mpmath
       - run: bin/test --force-colors --split=1/2
 
-  # -------------------- Test split 2/2 ---------------------------- #
+  # -------------------- Test split 2/2 older Python --------------- #
 
   tests2:
-    needs: code-quality
+    needs: [doctests-latest, tests1-latest, tests2-latest]
 
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        python-version: [3.6, 3.7, 3.8]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
@@ -82,34 +129,38 @@ jobs:
   # -------------------- Slow test split 1/2 ----------------------- #
 
   slow1:
-    needs: code-quality
+    needs: [doctests-latest, tests1-latest, tests2-latest]
+
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.9
       - run: python -m pip install --upgrade pip
       - run: pip install mpmath
       - run: TRAVIS_BUILD_NUMBER=true bin/test --force-colors --slow --timeout=595 --split=1/2
 
   # -------------------- Slow test split 2/2 ----------------------- #
 
   slow2:
-    needs: code-quality
+    needs: [doctests-latest, tests1-latest, tests2-latest]
+
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.9
       - run: python -m pip install --upgrade pip
       - run: pip install mpmath
       - run: TRAVIS_BUILD_NUMBER=true bin/test --force-colors --slow --timeout=595 --split=2/2
 
   # -------------------- Optional dependency tests ----------------- #
 
   optional-dependencies:
+    needs: [doctests-latest, tests1-latest, tests2-latest]
+
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
@@ -127,7 +178,8 @@ jobs:
   # -------------------- Build the html/latex docs ----------------- #
 
   sphinx:
-    needs: code-quality
+    needs: [doctests-latest, tests1-latest, tests2-latest]
+
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2