diff --git a/.github/workflows/e2e-dashboard-tests.yml b/.github/workflows/e2e-dashboard-tests.yml
index 051e6300..e12b9e3b 100644
--- a/.github/workflows/e2e-dashboard-tests.yml
+++ b/.github/workflows/e2e-dashboard-tests.yml
@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        optuna-version: ['optuna>=3.1.0', 'git+https://github.com/optuna/optuna.git']
+        optuna-version: ['optuna==3.1.0', 'git+https://github.com/optuna/optuna.git']
     steps:
       - uses: actions/checkout@v2
 
@@ -48,4 +48,4 @@ jobs:
 
       - name: Run e2e tests
         run: |
-          pytest e2e_tests/test_dashboard $ignore_option
+          pytest e2e_tests/test_dashboard
diff --git a/.github/workflows/python-tests.yml b/.github/workflows/python-tests.yml
index b1a7dbc8..a5f69159 100644
--- a/.github/workflows/python-tests.yml
+++ b/.github/workflows/python-tests.yml
@@ -18,7 +18,6 @@ jobs:
           python-version: '3.10'
           architecture: x64
       - name: Install dependencies
-        # python_tests requires optuna>=3.0.0 since it imports FloatDistribution
         run: |
           python -m pip install --progress-bar off --upgrade pip setuptools
           pip install --progress-bar off "optuna>=3.1.0"
@@ -32,10 +31,8 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        # Add Python '3.11' after released Optuna v3.1
-        # since Optuna v3.0.4 depends on scipy<1.9.0 and >=1.7.0
         python-version: ['3.7', '3.8', '3.9', '3.10', '3.11']
-        optuna-version: ['optuna>=3.1.0', 'git+https://github.com/optuna/optuna.git']
+        optuna-version: ['optuna>=3.1.0']
     steps:
       - uses: actions/checkout@v2
       - name: Setup Python${{ matrix.python-version }}
@@ -52,4 +49,44 @@ jobs:
           pip install --progress-bar off .[optional]
           pip install --progress-bar off .[test]
           pip install --progress-bar off .
-      - run: pytest python_tests
\ No newline at end of file
+      - name: Run python unit tests
+        run: |
+          pytest python_tests
+  test-with-optuna-master:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+          architecture: x64
+      - name: Install dependencies
+        run: |
+          python -m pip install --progress-bar off --upgrade pip setuptools
+          pip install --progress-bar off .[optional]
+          pip install --progress-bar off .[test]
+          pip install --progress-bar off .
+          python -m pip install --progress-bar off --upgrade git+https://github.com/optuna/optuna.git
+      - name: Run python unit tests
+        run: |
+          pytest python_tests
+  test-with-optuna-oldest: # Ideally, optuna==3.1.0, but lots of tests are broken.
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+          architecture: x64
+      - name: Install dependencies
+        run: |
+          python -m pip install --progress-bar off --upgrade pip setuptools
+          pip install --progress-bar off .[optional]
+          pip install --progress-bar off .[test]
+          pip install --progress-bar off .
+          python -m pip install --progress-bar off --upgrade optuna==3.4.0
+      - name: Run python unit tests
+        run: |
+          pytest python_tests