diff --git a/.github/workflows/check.yaml b/.github/workflows/check.yaml
new file mode 100644
index 0000000..2137b34
--- /dev/null
+++ b/.github/workflows/check.yaml
@@ -0,0 +1,25 @@
+name: "Check Codebase"
+
+on:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  check:
+    runs-on: "ubuntu-latest"
+
+    steps:
+      - name: "Checkout Codebase"
+        uses: "actions/checkout@v4"
+
+      - name: "Install nix"
+        uses: "cachix/install-nix-action@v25"
+        with:
+          nix_path: "nixpkgs=channel:nixos-23.11"
+
+      - name: "Use magic Nix cache"
+        uses: "DeterminateSystems/magic-nix-cache-action@v3"
+
+      - name: "Check"
+        run: |
+          nix-shell --run "dev-test-build"
diff --git a/.prettierrc.json b/.prettierrc.json
index e7ffdfe..aae5213 100644
--- a/.prettierrc.json
+++ b/.prettierrc.json
@@ -2,5 +2,13 @@
   "tabWidth": 2,
   "singleQuote": false,
   "trailingComma": "es5",
-  "printWidth": 120
+  "printWidth": 120,
+  "overrides": [
+    {
+      "files": "package.yaml",
+      "options": {
+        "singleQuote": true
+      }
+    }
+  ]
 }
diff --git a/README.md b/README.md
index af27b02..ee38753 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ The codebase comes with a Nix shell. You can use `direnv` for conveience:
 direnv allow
 ```
 
-Big, long build command for the impatient:
+Big, long format, lint, build and test command for the impatient:
 
 ```sh
 hpack &&
@@ -25,4 +25,10 @@ hpack &&
     cabal haddock -O0
 ```
 
+For testing and building:
+
+```sh
+dev-test-build
+```
+
 <!-- REFERENCES -->
diff --git a/default.nix b/default.nix
index 313d5a0..c6e9684 100644
--- a/default.nix
+++ b/default.nix
@@ -65,6 +65,26 @@ let
   ## SHELL ##
   ###########
 
+  dev-test-build = pkgs.writeShellScriptBin "dev-test-build" ''
+    #!/usr/bin/env bash
+
+    ## Fail on any error:
+    set -e
+
+    ## Show commands executed:
+    set -x
+
+    hpack
+    fourmolu --mode check app/ src/ test/
+    prettier --check .
+    find . -iname "*.nix" -not -path "*/nix/sources.nix" -print0 | xargs --null nixpkgs-fmt --check
+    hlint app/ src/ test/
+    cabal build -O0
+    cabal run -O0 lhp -- --version
+    cabal v1-test
+    cabal haddock -O0
+  '';
+
   ## Prepare Nix shell:
   thisShell = thisHaskell.shellFor {
     ## Define packages for the shell:
@@ -91,6 +111,9 @@ let
       pkgs.nil
       pkgs.nixpkgs-fmt
       pkgs.nodePackages.prettier
+
+      ## Our custom scripts:
+      dev-test-build
     ];
   };
 
diff --git a/release-please-config.json b/release-please-config.json
index ab63ce0..df9d6fb 100644
--- a/release-please-config.json
+++ b/release-please-config.json
@@ -10,9 +10,7 @@
       "draft": false,
       "prerelease": false,
       "initial-version": "0.0.1",
-      "extra-files": [
-        "package.yaml"
-      ]
+      "extra-files": ["package.yaml"]
     }
   }
 }