MAINT: Add OSX and Windows build to tests (#533)

Author: choldgraf

.github/workflows/tests.yml

@@ -16,13 +16,19 @@ jobs:
   # Build docs on a number of Python versions. In the future this can be
   # where tests go.
   tests:
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
+        os: [ubuntu-latest]
         python-version: [3.7, 3.8, 3.9, "3.10"]
+        # Manually specify one OSX + Windows build to make sure it works there.
         include:
           - python-version: "3.10"
             dev: true
+          - os: macos-latest
+            python-version: "3.9"
+          - os: windows-latest
+            python-version: "3.9"
 
     steps:
       - uses: actions/checkout@v2
@@ -46,7 +52,6 @@ jobs:
       # Build the docs
       - name: Build docs to store
         run: |
-          export PATH="$HOME/miniconda/bin:$PATH"
           sphinx-build -b html docs/ docs/_build/html -W --keep-going
 
       # Run tests under coverage
@@ -102,7 +107,6 @@ jobs:
       # Build the docs
       - name: Build docs to store
         run: |
-          export PATH="$HOME/miniconda/bin:$PATH"
           sphinx-build -b html docs/ docs/_build/html -W --keep-going
 
       # Serve the docs and wait to be ready