test: add basic test for flakeModule functionality

tests/fixtures/flake_parts/flake.lock

@@ -0,0 +1,77 @@
+{
+  "nodes": {
+    "flake-parts": {
+      "inputs": {
+        "nixpkgs-lib": "nixpkgs-lib"
+      },
+      "locked": {
+        "lastModified": 1754487366,
+        "narHash": "sha256-pHYj8gUBapuUzKV/kN/tR3Zvqc7o6gdFB9XKXIp1SQ8=",
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "rev": "af66ad14b28a127c5c0f3bbb298218fc63528a18",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "flake-parts",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1756636162,
+        "narHash": "sha256-mBecwgUTWRgClJYqcF+y4O1bY8PQHqeDpB+zsAn+/zA=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "37ff64b7108517f8b6ba5705ee5085eac636a249",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs-lib": {
+      "locked": {
+        "lastModified": 1753579242,
+        "narHash": "sha256-zvaMGVn14/Zz8hnp4VWT9xVnhc8vuL3TStRqwk22biA=",
+        "owner": "nix-community",
+        "repo": "nixpkgs.lib",
+        "rev": "0f36c44e01a6129be94e3ade315a5883f0228a6e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "nixpkgs.lib",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-parts": "flake-parts",
+        "nixpkgs": "nixpkgs",
+        "systems": "systems"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1689347949,
+        "narHash": "sha256-12tWmuL2zgBgZkdoB6qXZsgJEH9LR3oUgpaQq2RbI80=",
+        "owner": "nix-systems",
+        "repo": "default-linux",
+        "rev": "31732fcf5e8fea42e59c2488ad31a0e651500f68",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default-linux",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

tests/fixtures/flake_parts/flake.nix

@@ -0,0 +1,41 @@
+{
+  outputs = {
+    flake-parts,
+    systems,
+    ...
+  } @ inputs:
+    flake-parts.lib.mkFlake {inherit inputs;} {
+      imports = [
+        "@repo_path@/lib/flakeModule.nix"
+      ];
+      systems = import systems;
+      flake = {};
+      perSystem = _: {
+        ci = {
+          config = {
+            # true is already default, just for testing
+            nixJobsByDefault = true;
+          };
+          pipelines = {
+            "default" = {
+              stages = ["example"];
+              jobs."example" = {
+                stage = "example";
+                script = ["echo hello world"];
+              };
+            };
+            "test".jobs."example" = {
+              stage = ".pre";
+              script = ["echo hello world"];
+            };
+          };
+        };
+      };
+    };
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    flake-parts.url = "github:hercules-ci/flake-parts";
+    systems.url = "github:nix-systems/default-linux";
+  };
+}

tests/flake_parts_test.nix

@@ -0,0 +1,39 @@
+{
+  pkgs,
+  ntlib,
+  ...
+}: {
+  suites."flake-parts" = {
+    pos = __curPos;
+    tests = [
+      {
+        name = "flakeModule";
+        type = "script";
+        script =
+          # sh
+          ''
+            ${ntlib.helpers.scriptHelpers}
+            ${ntlib.helpers.path (with pkgs; [coreutils nix gnused gnugrep jq])}
+            repo_path=${../.}
+
+            dir=$(mktemp -d)
+            trap "rm -rf $dir" EXIT
+            cd $dir
+            cp ${./fixtures/flake_parts}/* .
+            # import from the absolute path above, is easier than trying to figure out the repo path etc.
+            sed -i -e "s|@repo_path@|$repo_path|" flake.nix
+
+            # NOTE: --impure is required since importing modules from absolute paths is not allowed in pure mode
+            nix build --impure .#gitlab-ci:pipeline:default
+            assert "-f result" "should exist"
+            assert_file_contains "result" "finalize_nix_ci"
+            jq '.' result  # check if valid json just to be sure
+
+            nix build --impure .#gitlab-ci:pipeline:default:pretty
+            assert "-f result" "should exist"
+            assert_file_contains "result" "  - finalize_nix_ci"
+          '';
+      }
+    ];
+  };
+}