use a nix package as test

.woodpecker/build_backend.yaml

@@ -0,0 +1,11 @@
+when:
+  - event: pull_request
+
+steps:
+  - name: "Run cargo test"
+    image: nixos/nix
+    commands:
+      - echo 'experimental-features = flakes nix-command' >> /etc/nix/nix.conf
+      - nix build --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt .#backend
+    volumes:
+      - /nix:/mnt/nix:ro

.woodpecker/cargo_clippy.yaml

@@ -3,7 +3,7 @@ when:
 
 steps:
   - name: "Run cargo clippy"
-    image: docker.nix-community.org/nixpkgs/nix-flakes
+    image: nixos/nix
     commands:
       - echo 'experimental-features = flakes nix-command' >> /etc/nix/nix.conf
       - nix develop --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt

.woodpecker/cargo_test.yaml

@@ -3,7 +3,7 @@ when:
 
 steps:
   - name: "Run cargo test"
-    image: docker.nix-community.org/nixpkgs/nix-flakes
+    image: nixos/nix
     commands:
       - echo 'experimental-features = flakes nix-command' >> /etc/nix/nix.conf
       - nix develop --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt

.woodpecker/check_fmt.yaml

@@ -3,7 +3,7 @@ when:
 
 steps:
   - name: "Run treefmt"
-    image: docker.nix-community.org/nixpkgs/nix-flakes
+    image: nixos/nix
     commands:
       - echo 'experimental-features = flakes nix-command' >> /etc/nix/nix.conf
       - nix fmt --store unix:///mnt/nix/var/nix/daemon-socket/socket?root=/mnt -- --fail-on-change

flake.nix

@@ -80,6 +80,28 @@
               };
             };
           };
+          backend = pkgs.rustPlatform.buildRustPackage rec {
+            pname = "backend";
+            version = "0.1";
+
+            src = pkgs.lib.fileset.toSource {
+              root = ./.;
+              fileset = pkgs.lib.fileset.unions [
+                ./Cargo.lock
+                ./Cargo.toml
+                ./crates
+                ./.cargo
+              ];
+            };
+
+            cargoLock = {
+              lockFile = ./Cargo.lock;
+            };
+
+            meta = {
+              mainProgram = "backend";
+            };
+          };
         }
       );
       formatter = forSystems (