diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..1088950
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,17 @@
+name: "CI/CD"
+
+"on":
+  push: {}
+
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v9
+      -
+        name: "Test: integration test"
+        run: nix flake check
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..3093a13
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,125 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1710146030,
+        "narHash": "sha256-SZ5L6eA7HJ/nmkzGG7/ISclqe6oZdOZTNoesiInkXPQ=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "b1d9ab70662946ef0850d488da1c9019f3a9752a",
+        "type": "github"
+      },
+      "original": {
+        "id": "flake-utils",
+        "type": "indirect"
+      }
+    },
+    "flake-utils_2": {
+      "inputs": {
+        "systems": "systems_2"
+      },
+      "locked": {
+        "lastModified": 1701680307,
+        "narHash": "sha256-kAuep2h5ajznlPMD9rnQyffWG8EM/C73lejGofXvdM8=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "4022d587cbbfd70fe950c1e2083a02621806a725",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1710066242,
+        "narHash": "sha256-bO7kahLdawW7rBqUTfWgf9mdPYrnOo5DGvWRJa9N8Do=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "db339f1706f555794b71aa4eb26a5a240fb6a599",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1703499205,
+        "narHash": "sha256-lF9rK5mSUfIZJgZxC3ge40tp1gmyyOXZ+lRY3P8bfbg=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "e1fa12d4f6c6fe19ccb59cac54b5b3f25e160870",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs",
+        "tomono": "tomono"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "systems_2": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "tomono": {
+      "inputs": {
+        "flake-utils": "flake-utils_2",
+        "nixpkgs": "nixpkgs_2"
+      },
+      "locked": {
+        "lastModified": 1709233426,
+        "narHash": "sha256-aXCsAxmxAydDuQrOxOKvfazbyW21d4R0wVNYLuTMQ4k=",
+        "owner": "hraban",
+        "repo": "tomono",
+        "rev": "ea66e5a0a76de4f6625b99e100cb5bdc120e82b0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hraban",
+        "repo": "tomono",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..ceb4d58
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,23 @@
+{
+  inputs = {
+    tomono.url = "github:hraban/tomono";
+  };
+
+  outputs = {
+    self, nixpkgs, flake-utils, tomono
+  }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+      in
+        {
+          checks.default = with pkgs; stdenvNoCC.mkDerivation {
+            name = "test";
+            checkPhase = writeShellScript "test" (builtins.readFile ./test.sh);
+            doCheck = true;
+            dontUnpack = true;
+            nativeBuildInputs = [ moreutils git tomono.packages.${system}.default ];
+            installPhase = "touch $out";
+          };
+        });
+  }
diff --git a/test.sh b/test.sh
new file mode 100755
index 0000000..657c804
--- /dev/null
+++ b/test.sh
@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+set -x
+
+# Ensure testing always works even on unconfigured CI etc
+export GIT_AUTHOR_NAME="Test"
+export GIT_AUTHOR_EMAIL="test@test.com"
+export GIT_COMMITTER_NAME="Test"
+export GIT_COMMITTER_EMAIL="test@test.com"
+
+d="$(mktemp -d)"
+cd "$d"
+pwd
+
+mkdir a
+(
+	cd a
+	git init
+	(for i in {1..9} ; do echo $i ; done) > count.txt
+	git add count.txt
+	git commit -m "count from 1 to 9"
+	git checkout -b more-numbers
+	echo 10 >> count.txt
+	git add count.txt
+	git commit -m "append 10"
+)
+
+echo "$PWD/a" a | tomono
+
+(
+	cd core/a
+	# In master
+	(echo 0; cat count.txt) | sponge count.txt
+	git add count.txt
+	git commit -m "count from 0"
+	# Continue dev
+	git checkout more-numbers
+	echo 11 >> count.txt
+	git add count.txt
+	git commit -m "count to 11"
+	# Merge it all
+	git checkout master
+	git merge more-numbers -m "merge dev"
+)
+
+echo "Finished dev:"
+cat core/a/count.txt