diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..17085b9
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,24 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+    paths-ignore:
+      - "README.md"
+  schedule:
+    - cron: "0 12 15 * *"
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+
+      - uses: cachix/install-nix-action@6ed004b9ccb68dbc28e7c85bee15fa93dbd214ac # v22
+        with:
+          nix_path: nixpkgs=channel:nixos-23.05
+
+      - run: |
+          ./run ci:test
diff --git a/run b/run
index 3aad137..6e37c92 100755
--- a/run
+++ b/run
@@ -32,6 +32,11 @@ function build {
   # TODO: build a Nix derivation and add it to the store.
 }
 
+function ci:test {
+  nix develop --command composer install
+  nix develop --command phpunit
+}
+
 # Display a list of all available commands.
 function help {
   printf "%s <task> [args]\n\nTasks:\n" "${0}"