Fix continuous integration (#8)

.github/workflows/unittest.yml

@@ -7,19 +7,15 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     steps:
     - uses: actions/checkout@v4
-    - name: Setup Mambaforge
-      uses: conda-incubator/setup-miniconda@v2
+    - uses: conda-incubator/setup-miniconda@v3
       with:
-        python-version: '3.11'
-        miniforge-variant: Mambaforge
-        channels: conda-forge
-        channel-priority: strict
-        activate-environment: my-env
+        auto-update-conda: true
+        python-version: "3.11"
         environment-file: environment.yml
-        use-mamba: true
+        auto-activate-base: false
     - name: Test
       shell: bash -l {0}
       timeout-minutes: 60

environment.yml

@@ -9,3 +9,4 @@ dependencies:
 - matplotlib =3.8.4
 - pygraphviz =1.13
 - networkx =3.3
+- mamba