Switch from setup-python to setup-micromamba

Easier to install CuPy (without CUDA libs) from conda-forge instead of PyPI.

.github/workflows/ci-tests.yml

@@ -17,23 +17,35 @@ jobs:
       matrix:
         python-version: ["3.10", "3.12"]
         os: [ubuntu-24.04]
+    defaults:
+      run:
+        shell: bash -l {0}
 
     steps:
       # Checkout current git repository
       - name: Checkout
         uses: actions/checkout@v4.1.7
 
-      # Install Python
-      - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v5.1.0
+      # Install Micromamba with conda-forge dependencies
+      - name: Setup Micromamba
+        uses: mamba-org/setup-micromamba@v1.9.0
         with:
-          python-version: ${{ matrix.python-version }}
+          environment-name: cupy-xarray
+          condarc: |
+            channels:
+              - conda-forge
+              - nodefaults
+          create-args: >-
+            cupy-core
+            dask
+            pip
+            python=${{ matrix.python-version }}
+            pytest
+            xarray
 
-      # Install dependencies from requirements.txt file
-      - name: Install dependencies
-        run: |
-          python -m pip install --upgrade pip
-          CUPY_NO_CUDA=true python -m pip install .[test]
+      # Install the package that we want to test
+      - name: Install the package
+        run: python -m pip install .
 
       # Run the unit tests
       - name: Test with pytest