caching environment for test routine

.github/workflows/test.yml

@@ -28,6 +28,39 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  caching-environment:
+    name: caching
+    runs-on: "ubuntu-latest" # FIXME: not sure what it should run on
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup Mambaforge
+        uses: conda-incubator/setup-miniconda@v2
+        with:
+            miniforge-variant: Mambaforge
+            miniforge-version: latest
+            activate-environment: anaconda-client-env
+            use-mamba: true
+
+      - name: Get Date
+        id: get-date
+        run: echo "::set-output name=today::$(/bin/date -u '+%Y%m%d')"
+        shell: bash
+
+      - name: Cache Conda env
+        uses: actions/cache@v2
+        with:
+          path: ${{ env.CONDA }}/envs
+          key: conda-${{ runner.os }}--${{ runner.arch }}--${{ steps.get-date.outputs.today }}-${{ hashFiles('etc/environment-caching.yml') }}-${{ env.CACHE_NUMBER }}
+        env:
+          # Increase this value to reset cache if etc/environment.yml has not changed
+          CACHE_NUMBER: 0
+        id: cache
+
+      - name: Update environment
+        run: mamba env update -n anaconda-client-env -f etc/environment-caching.yml
+        if: steps.cache.outputs.cache-hit != 'true'
+
   # Look into replacing this with pre-commit.ci
   code-quality:
     runs-on: ubuntu-latest
@@ -59,7 +92,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
-      - uses: conda-incubator/setup-miniconda@v2
+      - uses: conda-incubator/setup-miniconda@v2 # FIXME: reference cached environment here?
         name: Set up conda
         with:
           # We want to come back and add a previous step (maybe our own github action)