Add GitHub actions.

.github/workflows/tests.yml

@@ -0,0 +1,49 @@
+jobs:
+  test:
+    strategy:
+      matrix:
+        platform:
+         - os: ubuntu-latest
+           miniconda-url: https://github.com/conda-forge/miniforge/releases/latest/download/Mambaforge-Linux-x86_64.sh
+         - os: macos-latest
+           miniconda-url: https://github.com/conda-forge/miniforge/releases/latest/download/Mambaforge-MacOSX-x86_64.sh
+         - os: windows-latest
+           miniconda-url: https://github.com/conda-forge/miniforge/releases/latest/download/Mambaforge-Windows-x86_64.exe
+        python: [3.7, 3.8, 3.9]
+    runs-on: ${{ matrix.os }}
+    env:
+      PYTHON_VERSION: ${{ matrix.python }}
+
+  steps:
+    - name: Checkout Repo
+      uses: actions/checkout@v2
+    - uses: conda-incubator/setup-miniconda@v2
+      with:
+        installer-url: ${{ matrix.miniconda-url }}
+        activate-environment: sparse-dev
+        allow-softlinks: true
+    - name: Install package
+      run: |
+        conda create -n sparse-dev python=$PYTHON_VERSION
+        pip install -e .[tests]
+        pip install codecov
+    - name: Run tests
+      run: |
+        pytest --pyargs sparse
+    - uses: codecov/codecov-action@v1
+on:
+  # Trigger the workflow on push or pull request,
+  # but only for the main branch
+  push:
+    branches:
+      - main
+      - vnext
+  pull_request:
+    branches:
+      - main
+      - vnext
+  # Also trigger on page_build, as well as release created events
+  page_build:
+  release:
+    types: # This configuration does not affect the page_build event above
+      - created