Add GHA CI

Adds linting and tests to CI.

Author: TylerWitt

.github/workflows/ci.yml

@@ -0,0 +1,103 @@
+name: Linting & Tests
+
+# Define workflow that runs when changes are pushed to the
+# `main` branch or pushed to a PR branch that targets the `main`
+# branch. Change the branch name if your project uses a
+# different name for the main branch like "master" or "production".
+on:
+  push:
+    branches: [ "main" ] 
+  pull_request:
+    branches: [ "main" ] 
+
+# Sets the ENV `MIX_ENV` to `test` for running tests
+env:
+  MIX_ENV: test
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    name: Test on OTP ${{matrix.otp}} / Elixir ${{matrix.elixir}}
+    strategy:
+      # Specify the OTP and Elixir versions to use when building
+      # and running the workflow steps.
+      matrix:
+        otp: ['25.0.4', '27.2']       # Define the OTP version [required]
+        elixir: ['1.14.1', '1.18.4']    # Define the elixir version [required]
+        exclude:
+          - otp: '27.2'
+            elixir: '1.14.1'
+    steps:
+    # Step: Setup Elixir + Erlang image as the base.
+    - name: Set up Elixir
+      uses: erlef/setup-beam@v1
+      with:
+        otp-version: ${{matrix.otp}}
+        elixir-version: ${{matrix.elixir}}
+
+    # Step: Check out the code.
+    - name: Checkout code
+      uses: actions/checkout@v4
+
+    # Step: Define how to cache deps. Restores existing cache if present.
+    - name: Cache deps
+      id: cache-deps
+      uses: actions/cache@v3
+      env:
+        cache-name: cache-elixir-deps
+      with:
+        path: deps
+        key: ${{ runner.os }}-mix-${{ env.cache-name }}-${{ hashFiles('**/mix.lock') }}
+        restore-keys: |
+          ${{ runner.os }}-mix-${{ env.cache-name }}-
+
+    # Step: Define how to cache the `_build` directory. After the first run,
+    # this speeds up tests runs a lot. This includes not re-compiling our
+    # project's downloaded deps every run.
+    - name: Cache compiled build
+      id: cache-build
+      uses: actions/cache@v3
+      env:
+        cache-name: cache-compiled-build
+      with:
+        path: _build
+        key: ${{ runner.os }}-mix-${{ env.cache-name }}-${{ hashFiles('**/mix.lock') }}
+        restore-keys: |
+          ${{ runner.os }}-mix-${{ env.cache-name }}-
+          ${{ runner.os }}-mix-
+
+    # Step: Conditionally bust the cache when job is re-run.
+    # Sometimes, we may have issues with incremental builds that are fixed by
+    # doing a full recompile. In order to not waste dev time on such trivial
+    # issues (while also reaping the time savings of incremental builds for
+    # *most* day-to-day development), force a full recompile only on builds
+    # that are retried.
+    - name: Clean to rule out incremental build as a source of flakiness
+      if: github.run_attempt != '1'
+      run: |
+        mix deps.clean --all
+        mix clean
+      shell: sh
+
+    # Step: Download project dependencies. If unchanged, uses
+    # the cached version.
+    - name: Install dependencies
+      run: mix deps.get
+
+    # Step: Compile the project treating any warnings as errors.
+    # Customize this step if a different behavior is desired.
+    - name: Compiles without warnings
+      run: mix compile --warnings-as-errors
+
+    # Step: Check that the checked in code has already been formatted.
+    # This step fails if something was found unformatted.
+    # Customize this step as desired.
+    - name: Check Formatting
+      run: mix format --check-formatted
+
+    # Step: Execute the tests.
+    - name: Run tests
+      run: mix test