dockerTools: Test changing compression of `buildLayeredImage`

nixos/tests/docker-tools.nix

···
             "docker load --input='${examples.bashUncompressed}'",
             "docker rmi ${examples.bashUncompressed.imageName}",
         )
+        docker.succeed(
+            "docker load --input='${examples.bashLayeredUncompressed}'",
+            "docker rmi ${examples.bashLayeredUncompressed.imageName}",
+        )
+        docker.succeed(
+            "docker load --input='${examples.bashLayeredZstdCompressed}'",
+            "docker rmi ${examples.bashLayeredZstdCompressed.imageName}",
+        )
 
     with subtest(
         "Check if the nix store is correctly initialized by listing "

pkgs/build-support/docker/examples.nix

···
     contents = pkgs.bashInteractive;
   };
 
-  # buildImage without explicit tag
+  # buildLayeredImage without compression
+  bashLayeredUncompressed = pkgs.dockerTools.buildLayeredImage {
+    name = "bash-layered-uncompressed";
+    tag = "latest";
+    compressor = "none";
+    contents = pkgs.bashInteractive;
+  };
+
+  # buildLayeredImage with zstd compression
+  bashLayeredZstdCompressed = pkgs.dockerTools.buildLayeredImage {
+    name = "bash-layered-zstd";
+    tag = "latest";
+    compressor = "zstd";
+    contents = pkgs.bashInteractive;
+  };
+
+  # streamLayeredImage without explicit tag
   bashNoTagStreamLayered = pkgs.dockerTools.streamLayeredImage {
     name = "bash-no-tag-stream-layered";
     contents = pkgs.bashInteractive;