Merge pull request #31 from imjasonh/fix/layered-image-building

Fix layered image building with cross-registry support

example/hello-krust/src/main.rs

@@ -1,4 +1,17 @@
 fn main() {
     println!("Hello from krust example!");
-    println!("This is running inside a container built with krust.");
+    println!("Current architecture: {}", std::env::consts::ARCH);
+
+    // Check for SSL_CERT_FILE environment variable (common in distroless images)
+    match std::env::var("SSL_CERT_FILE") {
+        Ok(value) => println!("✓ SSL_CERT_FILE found: {}", value),
+        Err(_) => panic!("✗ SSL_CERT_FILE not found (base image env not preserved)"),
+    }
+
+    // Check for /etc/os-release file (common in most Linux base images)
+    if std::path::Path::new("/etc/os-release").exists() {
+        println!("✓ /etc/os-release found (base image layers preserved)");
+    } else {
+        panic!("✗ /etc/os-release not found (base image layers not preserved)");
+    }
 }

src/image/mod.rs

@@ -1,6 +1,7 @@
 use anyhow::{Context, Result};
 use flate2::write::GzEncoder;
 use flate2::Compression;
+use oci_distribution::secrets::RegistryAuth;
 use serde::{Deserialize, Serialize};
 use sha256::digest;
 use std::fs::File;
@@ -8,27 +9,25 @@ use std::io::Write;
 use tar::Builder;
 use tracing::{debug, info};
 
-#[cfg(test)]
-mod tests;
-
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ImageConfig {
     pub architecture: String,
     pub os: String,
     pub config: Config,
     pub rootfs: RootFs,
+    #[serde(default)]
     pub history: Vec<History>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Config {
-    #[serde(rename = "Env")]
+    #[serde(rename = "Env", default)]
     pub env: Vec<String>,
     #[serde(rename = "Cmd")]
     pub cmd: Option<Vec<String>>,
-    #[serde(rename = "WorkingDir")]
+    #[serde(rename = "WorkingDir", default)]
     pub working_dir: String,
-    #[serde(rename = "User")]
+    #[serde(rename = "User", default)]
     pub user: String,
 }
 
@@ -43,7 +42,9 @@ pub struct RootFs {
 pub struct History {
     pub created: String,
     pub created_by: String,
+    #[serde(default)]
     pub comment: String,
+    #[serde(default)]
     pub empty_layer: bool,
 }
 
@@ -83,18 +84,49 @@ impl ImageBuilder {
         }
     }
 
-    pub fn build(&self) -> Result<(Vec<u8>, Vec<u8>, Manifest)> {
+    pub async fn build(
+        &self,
+        registry_client: &mut crate::registry::RegistryClient,
+        auth: &RegistryAuth,
+    ) -> Result<(Vec<u8>, Vec<u8>, Manifest)> {
         info!("Building container image");
 
-        let (os, arch) = self.parse_platform()?;
+        let (_os, _arch) = self.parse_platform()?;
+
+        // Fetch base image data
+        info!(
+            "Fetching base image: {} for platform: {}",
+            self.base_image, self.platform
+        );
+        let (base_manifest, base_config) = registry_client
+            .fetch_image_data(&self.base_image, &self.platform, auth)
+            .await
+            .context("Failed to fetch base image data")?;
 
         // Create application layer
-        let (layer_data, diff_id) = self.create_layer()?;
-        let layer_digest = format!("sha256:{}", digest(&layer_data));
-        let layer_size = layer_data.len() as i64;
+        let (app_layer_data, app_diff_id) = self.create_layer()?;
+        let app_layer_digest = format!("sha256:{}", digest(&app_layer_data));
+        let app_layer_size = app_layer_data.len() as i64;
 
-        // Create image config
-        let config = self.create_config(&os, &arch, &diff_id)?;
+        // Combine base image layers with application layer
+        let mut all_layers = Vec::new();
+        for layer in &base_manifest.layers {
+            all_layers.push(Descriptor {
+                media_type: layer.media_type.clone(),
+                size: layer.size,
+                digest: layer.digest.clone(),
+            });
+        }
+
+        // Add the application layer
+        all_layers.push(Descriptor {
+            media_type: "application/vnd.docker.image.rootfs.diff.tar.gzip".to_string(),
+            size: app_layer_size,
+            digest: app_layer_digest,
+        });
+
+        // Create merged config
+        let config = self.create_layered_config(&base_config, &app_diff_id)?;
         let config_data = serde_json::to_vec_pretty(&config)?;
         let config_digest = format!("sha256:{}", digest(&config_data));
         let config_size = config_data.len() as i64;
@@ -108,14 +140,10 @@ impl ImageBuilder {
                 size: config_size,
                 digest: config_digest,
             },
-            layers: vec![Descriptor {
-                media_type: "application/vnd.docker.image.rootfs.diff.tar.gzip".to_string(),
-                size: layer_size,
-                digest: layer_digest,
-            }],
+            layers: all_layers,
         };
 
-        Ok((config_data, layer_data, manifest))
+        Ok((config_data, app_layer_data, manifest))
     }
 
     fn parse_platform(&self) -> Result<(String, String)> {
@@ -163,7 +191,11 @@ impl ImageBuilder {
         Ok((compressed, diff_id))
     }
 
-    fn create_config(&self, os: &str, arch: &str, layer_digest: &str) -> Result<ImageConfig> {
+    fn create_layered_config(
+        &self,
+        base_config: &ImageConfig,
+        app_diff_id: &str,
+    ) -> Result<ImageConfig> {
         let binary_name = self
             .binary_path
             .file_name()
@@ -171,27 +203,225 @@ impl ImageBuilder {
             .to_str()
             .context("Invalid UTF-8 in binary name")?;
 
+        // Merge environment variables (preserve base + add our own)
+        let mut merged_env = base_config.config.env.clone();
+
+        // Add PATH if not present
+        if !merged_env.iter().any(|env| env.starts_with("PATH=")) {
+            merged_env.push(
+                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin".to_string(),
+            );
+        }
+
+        // Combine diff_ids (base layers + app layer)
+        let mut merged_diff_ids = base_config.rootfs.diff_ids.clone();
+        merged_diff_ids.push(app_diff_id.to_string());
+
+        // Combine history (base history + app history)
+        let mut merged_history = base_config.history.clone();
+        merged_history.push(History {
+            created: chrono::Utc::now().to_rfc3339(),
+            created_by: "krust".to_string(),
+            comment: "Built with krust".to_string(),
+            empty_layer: false,
+        });
+
         Ok(ImageConfig {
-            architecture: arch.to_string(),
-            os: os.to_string(),
+            architecture: base_config.architecture.clone(),
+            os: base_config.os.clone(),
             config: Config {
-                env: vec![
-                    "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin".to_string(),
-                ],
+                env: merged_env,
                 cmd: Some(vec![format!("/app/{}", binary_name)]),
-                working_dir: "/".to_string(),
-                user: "65532:65532".to_string(), // nonroot user
+                working_dir: base_config.config.working_dir.clone(),
+                user: base_config.config.user.clone(),
             },
             rootfs: RootFs {
                 fs_type: "layers".to_string(),
-                diff_ids: vec![layer_digest.to_string()],
+                diff_ids: merged_diff_ids,
             },
-            history: vec![History {
-                created: chrono::Utc::now().to_rfc3339(),
-                created_by: "krust".to_string(),
-                comment: "Built with krust".to_string(),
-                empty_layer: false,
-            }],
+            history: merged_history,
         })
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Write;
+    use std::path::PathBuf;
+    use tempfile::NamedTempFile;
+
+    fn create_test_binary() -> PathBuf {
+        let mut temp_file = NamedTempFile::new().unwrap();
+        temp_file.write_all(b"fake binary content").unwrap();
+        let path = temp_file.path().to_path_buf();
+        // Keep the file alive by converting to a regular file
+        std::fs::copy(&path, &path).unwrap();
+        path
+    }
+
+    fn create_base_image_config() -> ImageConfig {
+        ImageConfig {
+            architecture: "amd64".to_string(),
+            os: "linux".to_string(),
+            config: Config {
+                env: vec![
+                    "PATH=/usr/local/bin:/usr/bin:/bin".to_string(),
+                    "SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt".to_string(),
+                ],
+                cmd: None,
+                working_dir: "/".to_string(),
+                user: "nonroot:nonroot".to_string(),
+            },
+            rootfs: RootFs {
+                fs_type: "layers".to_string(),
+                diff_ids: vec![
+                    "sha256:base_layer_1".to_string(),
+                    "sha256:base_layer_2".to_string(),
+                ],
+            },
+            history: vec![
+                History {
+                    created: "2023-01-01T00:00:00Z".to_string(),
+                    created_by: "base-image-builder".to_string(),
+                    comment: "Base layer 1".to_string(),
+                    empty_layer: false,
+                },
+                History {
+                    created: "2023-01-01T00:01:00Z".to_string(),
+                    created_by: "base-image-builder".to_string(),
+                    comment: "Base layer 2".to_string(),
+                    empty_layer: false,
+                },
+            ],
+        }
+    }
+
+    #[test]
+    fn test_parse_platform() {
+        let builder = ImageBuilder::new(
+            PathBuf::from("/tmp/test"),
+            "test-base".to_string(),
+            "linux/amd64".to_string(),
+        );
+
+        let (os, arch) = builder.parse_platform().unwrap();
+        assert_eq!(os, "linux");
+        assert_eq!(arch, "amd64");
+    }
+
+    #[test]
+    fn test_create_layered_config_preserves_base_environment() {
+        let binary_path = create_test_binary();
+        let builder = ImageBuilder::new(
+            binary_path,
+            "test-base".to_string(),
+            "linux/amd64".to_string(),
+        );
+
+        let base_config = create_base_image_config();
+        let app_diff_id = "sha256:app_layer_diff_id";
+
+        let result = builder
+            .create_layered_config(&base_config, app_diff_id)
+            .unwrap();
+
+        // Check that base environment variables are preserved
+        assert!(result
+            .config
+            .env
+            .contains(&"SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt".to_string()));
+        assert!(result.config.env.iter().any(|env| env.starts_with("PATH=")));
+
+        // Check that working directory is preserved
+        assert_eq!(result.config.working_dir, "/");
+
+        // Check that user is preserved
+        assert_eq!(result.config.user, "nonroot:nonroot");
+
+        // Check that architecture and OS are preserved
+        assert_eq!(result.architecture, "amd64");
+        assert_eq!(result.os, "linux");
+    }
+
+    #[test]
+    fn test_create_layered_config_combines_diff_ids() {
+        let binary_path = create_test_binary();
+        let builder = ImageBuilder::new(
+            binary_path,
+            "test-base".to_string(),
+            "linux/amd64".to_string(),
+        );
+
+        let base_config = create_base_image_config();
+        let app_diff_id = "sha256:app_layer_diff_id";
+
+        let result = builder
+            .create_layered_config(&base_config, app_diff_id)
+            .unwrap();
+
+        // Check that base diff_ids are preserved and app diff_id is appended
+        assert_eq!(result.rootfs.diff_ids.len(), 3);
+        assert_eq!(result.rootfs.diff_ids[0], "sha256:base_layer_1");
+        assert_eq!(result.rootfs.diff_ids[1], "sha256:base_layer_2");
+        assert_eq!(result.rootfs.diff_ids[2], "sha256:app_layer_diff_id");
+    }
+
+    #[test]
+    fn test_create_layered_config_combines_history() {
+        let binary_path = create_test_binary();
+        let builder = ImageBuilder::new(
+            binary_path,
+            "test-base".to_string(),
+            "linux/amd64".to_string(),
+        );
+
+        let base_config = create_base_image_config();
+        let app_diff_id = "sha256:app_layer_diff_id";
+
+        let result = builder
+            .create_layered_config(&base_config, app_diff_id)
+            .unwrap();
+
+        // Check that base history is preserved and app history is appended
+        assert_eq!(result.history.len(), 3);
+        assert_eq!(result.history[0].created_by, "base-image-builder");
+        assert_eq!(result.history[1].created_by, "base-image-builder");
+        assert_eq!(result.history[2].created_by, "krust");
+        assert_eq!(result.history[2].comment, "Built with krust");
+        assert!(!result.history[2].empty_layer);
+    }
+
+    #[test]
+    fn test_image_config_serialization_compatibility() {
+        // Test that our ImageConfig can deserialize from a realistic base image config
+        let json_config = r#"{
+            "architecture": "amd64",
+            "os": "linux",
+            "config": {
+                "Env": [
+                    "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
+                    "SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt"
+                ],
+                "WorkingDir": "/",
+                "User": "nonroot:nonroot"
+            },
+            "rootfs": {
+                "type": "layers",
+                "diff_ids": [
+                    "sha256:b49b96bfa4b2477b73b0b8fe5e4ce383aa1d0026c1e845fb5d43c1f0b8bdb6ac"
+                ]
+            }
+        }"#;
+
+        let parsed: ImageConfig = serde_json::from_str(json_config).unwrap();
+
+        assert_eq!(parsed.architecture, "amd64");
+        assert_eq!(parsed.os, "linux");
+        assert_eq!(parsed.config.env.len(), 2);
+        assert_eq!(parsed.config.working_dir, "/");
+        assert_eq!(parsed.config.user, "nonroot:nonroot");
+        assert_eq!(parsed.rootfs.diff_ids.len(), 1);
+        assert_eq!(parsed.history.len(), 0); // Default empty for missing field
+    }
+}

src/image/tests.rs

@@ -1,29 +0,0 @@
-#[cfg(test)]
-mod tests {
-    use super::super::*;
-    use std::path::PathBuf;
-
-    #[test]
-    fn test_parse_platform() {
-        let builder = ImageBuilder::new(
-            PathBuf::from("/tmp/test"),
-            "test-base".to_string(),
-            "linux/amd64".to_string(),
-        );
-
-        let (os, arch) = builder.parse_platform().unwrap();
-        assert_eq!(os, "linux");
-        assert_eq!(arch, "amd64");
-    }
-
-    #[test]
-    fn test_parse_platform_invalid() {
-        let builder = ImageBuilder::new(
-            PathBuf::from("/tmp/test"),
-            "test-base".to_string(),
-            "invalid-platform".to_string(),
-        );
-
-        assert!(builder.parse_platform().is_err());
-    }
-}

src/main.rs

@@ -120,20 +120,40 @@ async fn main() -> Result<()> {
                     platform_str.clone(),
                 );
 
-                let (config_data, layer_data, manifest) = image_builder.build()?;
+                // Always use layered approach - registry layer will handle cross-registry blob copying
+                let base_auth = resolve_auth(&base_image)?;
+                let (config_data, layer_data, manifest) = image_builder
+                    .build(&mut registry_client, &base_auth)
+                    .await?;
 
                 // Push platform-specific image if not --no-push
                 if !no_push {
                     info!("Pushing image for platform: {}", platform_str);
 
-                    let layers = vec![(layer_data, manifest.layers[0].media_type.clone())];
-
                     // Get auth for the target registry
                     let push_auth = resolve_auth(&target_repo)?;
 
-                    // Push platform image by digest only (no tags)
+                    // Get the media type of the application layer (last layer in manifest)
+                    let app_layer_media_type = manifest
+                        .layers
+                        .last()
+                        .map(|l| l.media_type.clone())
+                        .unwrap_or_else(|| {
+                            "application/vnd.docker.image.rootfs.diff.tar.gzip".to_string()
+                        });
+
+                    // Push layered image (copy base layers if needed + push app layer + manifest)
                     let (digest_ref, manifest_size) = registry_client
-                        .push_image_by_digest(&target_repo, config_data, layers, &push_auth)
+                        .push_layered_image(
+                            &target_repo,
+                            config_data,
+                            layer_data,
+                            app_layer_media_type,
+                            &manifest,
+                            &push_auth,
+                            &base_image,
+                            &base_auth,
+                        )
                         .await?;
 
                     // Parse platform string

src/registry/mod.rs

@@ -5,9 +5,6 @@ use oci_distribution::{Client, Reference};
 use std::str::FromStr;
 use tracing::{debug, info};
 
-#[cfg(test)]
-mod tests;
-
 pub struct RegistryClient {
     client: Client,
 }
@@ -269,6 +266,244 @@ impl RegistryClient {
         Ok(image_ref)
     }
 
+    /// Push a layered image where only the top layer is new
+    #[allow(clippy::too_many_arguments)]
+    pub async fn push_layered_image(
+        &mut self,
+        repository: &str,
+        config_data: Vec<u8>,
+        new_layer_data: Vec<u8>,
+        _new_layer_media_type: String,
+        manifest: &crate::image::Manifest,
+        auth: &RegistryAuth,
+        base_image_ref: &str,
+        base_auth: &RegistryAuth,
+    ) -> Result<(String, usize)> {
+        // Create a temporary reference for authentication
+        let temp_ref = format!("{}:temp", repository);
+        let reference: Reference = temp_ref
+            .parse()
+            .context("Failed to parse repository reference")?;
+
+        info!("Pushing layered image to {} (digest only)", repository);
+
+        // Authenticate with the registry
+        self.client
+            .auth(&reference, auth, oci_distribution::RegistryOperation::Push)
+            .await
+            .context("Failed to authenticate with registry")?;
+
+        // Push config blob
+        let config_digest = format!("sha256:{}", sha256::digest(&config_data));
+        debug!("Pushing config blob: {}", config_digest);
+
+        self.client
+            .push_blob(&reference, &config_data, &config_digest)
+            .await
+            .context("Failed to push config blob")?;
+
+        // Copy base image layers if they don't exist in target registry
+        let base_reference: Reference = base_image_ref
+            .parse()
+            .context("Failed to parse base image reference")?;
+
+        // Check if we need to copy base layers (cross-registry scenario)
+        let base_registry = base_reference.registry();
+        let target_registry = reference.registry();
+        let need_copy_layers = base_registry != target_registry;
+
+        if need_copy_layers {
+            info!(
+                "Copying base image layers from {} to {}",
+                base_registry, target_registry
+            );
+
+            // Authenticate with base image registry
+            let base_client = Client::new(oci_distribution::client::ClientConfig::default());
+            base_client
+                .auth(
+                    &base_reference,
+                    base_auth,
+                    oci_distribution::RegistryOperation::Pull,
+                )
+                .await
+                .context("Failed to authenticate with base registry")?;
+
+            // Copy each base layer (all except the last one which is our app layer)
+            for layer in &manifest.layers[..manifest.layers.len().saturating_sub(1)] {
+                debug!("Copying base layer: {}", layer.digest);
+
+                // Pull the layer from base registry
+                let mut layer_data = Vec::new();
+                let layer_descriptor = oci_distribution::manifest::OciDescriptor {
+                    media_type: layer.media_type.clone(),
+                    digest: layer.digest.clone(),
+                    size: layer.size,
+                    urls: None,
+                    annotations: None,
+                };
+
+                base_client
+                    .pull_blob(&base_reference, &layer_descriptor, &mut layer_data)
+                    .await
+                    .context("Failed to pull base layer")?;
+
+                // Push the layer to target registry
+                self.client
+                    .push_blob(&reference, &layer_data, &layer.digest)
+                    .await
+                    .context("Failed to push copied base layer")?;
+            }
+        }
+
+        // Push the new application layer
+        let new_layer_digest = format!("sha256:{}", sha256::digest(&new_layer_data));
+        debug!("Pushing new application layer: {}", new_layer_digest);
+
+        self.client
+            .push_blob(&reference, &new_layer_data, &new_layer_digest)
+            .await
+            .context("Failed to push new layer")?;
+
+        // Create manifest with all layers (base + new)
+        let mut manifest_layers = Vec::new();
+        for layer in &manifest.layers {
+            manifest_layers.push(oci_distribution::manifest::OciDescriptor {
+                media_type: layer.media_type.clone(),
+                digest: layer.digest.clone(),
+                size: layer.size,
+                urls: None,
+                annotations: None,
+            });
+        }
+
+        // Create and push manifest
+        let image_manifest = oci_distribution::manifest::OciImageManifest {
+            schema_version: 2,
+            media_type: Some("application/vnd.oci.image.manifest.v1+json".to_string()),
+            artifact_type: None,
+            config: oci_distribution::manifest::OciDescriptor {
+                media_type: "application/vnd.oci.image.config.v1+json".to_string(),
+                digest: config_digest,
+                size: config_data.len() as i64,
+                urls: None,
+                annotations: None,
+            },
+            layers: manifest_layers,
+            annotations: None,
+        };
+
+        // Wrap in OciManifest enum
+        let oci_manifest = oci_distribution::manifest::OciManifest::Image(image_manifest);
+
+        debug!("Pushing manifest for layered image");
+        let (manifest_url, digest) = self
+            .client
+            .push_manifest_and_get_digest(&reference, &oci_manifest)
+            .await
+            .context("Failed to push manifest")?;
+
+        info!(
+            "Successfully pushed layered image to {} (digest: {})",
+            manifest_url, digest
+        );
+
+        // Build the full image reference with digest only
+        let registry = reference.registry();
+        let repository = reference.repository();
+        let digest_ref = format!("{}/{}@{}", registry, repository, digest);
+
+        // Return both the digest ref and the actual manifest size
+        let manifest_size = serde_json::to_vec(&oci_manifest)?.len();
+        Ok((digest_ref, manifest_size))
+    }
+
+    /// Fetch the manifest and config for a specific platform of an image
+    pub async fn fetch_image_data(
+        &mut self,
+        image_ref: &str,
+        platform: &str,
+        auth: &RegistryAuth,
+    ) -> Result<(
+        oci_distribution::manifest::OciImageManifest,
+        crate::image::ImageConfig,
+    )> {
+        let reference: Reference = image_ref
+            .parse()
+            .context("Failed to parse image reference")?;
+
+        debug!(
+            "Fetching image data for {} platform {}",
+            reference, platform
+        );
+
+        // Authenticate with the registry
+        self.client
+            .auth(&reference, auth, oci_distribution::RegistryOperation::Pull)
+            .await
+            .context("Failed to authenticate with registry")?;
+
+        // Pull the manifest for the specific platform
+        let (manifest, _digest) = self
+            .client
+            .pull_manifest(&reference, auth)
+            .await
+            .context("Failed to pull manifest")?;
+
+        // Handle different manifest types
+        let image_manifest = match manifest {
+            oci_distribution::manifest::OciManifest::Image(img_manifest) => img_manifest,
+            oci_distribution::manifest::OciManifest::ImageIndex(index) => {
+                // Find the manifest for the requested platform
+                let (os, arch) = platform
+                    .split_once('/')
+                    .ok_or_else(|| anyhow::anyhow!("Invalid platform format: {}", platform))?;
+
+                let platform_manifest = index
+                    .manifests
+                    .iter()
+                    .find(|m| {
+                        m.platform
+                            .as_ref()
+                            .is_some_and(|p| p.os == os && p.architecture == arch)
+                    })
+                    .ok_or_else(|| {
+                        anyhow::anyhow!("Platform {} not found in image index", platform)
+                    })?;
+
+                // Pull the platform-specific manifest
+                let platform_ref = format!("{}@{}", image_ref, platform_manifest.digest);
+                let platform_reference: Reference = platform_ref
+                    .parse()
+                    .context("Failed to parse platform reference")?;
+
+                let (platform_manifest, _) = self
+                    .client
+                    .pull_manifest(&platform_reference, auth)
+                    .await
+                    .context("Failed to pull platform manifest")?;
+
+                match platform_manifest {
+                    oci_distribution::manifest::OciManifest::Image(img_manifest) => img_manifest,
+                    _ => anyhow::bail!("Expected image manifest, got index"),
+                }
+            }
+        };
+
+        // Pull the config blob
+        let mut config_data = Vec::new();
+        self.client
+            .pull_blob(&reference, &image_manifest.config, &mut config_data)
+            .await
+            .context("Failed to pull config blob")?;
+
+        // Parse the config
+        let config: crate::image::ImageConfig =
+            serde_json::from_slice(&config_data).context("Failed to parse image config")?;
+
+        Ok((image_manifest, config))
+    }
+
     /// Fetch the manifest for an image and extract available platforms
     pub async fn get_image_platforms(
         &mut self,
@@ -341,3 +576,91 @@ pub fn parse_image_reference(image: &str) -> Result<(String, String, String)> {
 
     Ok((registry, repository, tag))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::image::{Config, History, ImageConfig, RootFs};
+
+    #[test]
+    fn test_parse_image_reference() {
+        let (registry, repo, tag) =
+            parse_image_reference("docker.io/library/hello-world:latest").unwrap();
+        assert_eq!(registry, "docker.io");
+        assert_eq!(repo, "library/hello-world");
+        assert_eq!(tag, "latest");
+    }
+
+    #[test]
+    fn test_parse_image_reference_no_tag() {
+        let (_, _, tag) = parse_image_reference("docker.io/library/hello-world").unwrap();
+        assert_eq!(tag, "latest");
+    }
+
+    #[test]
+    fn test_layered_config_structure() {
+        // Test layered config creation
+        let config = ImageConfig {
+            architecture: "amd64".to_string(),
+            os: "linux".to_string(),
+            config: Config {
+                env: vec![
+                    "PATH=/usr/local/bin:/usr/bin:/bin".to_string(),
+                    "SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt".to_string(),
+                ],
+                cmd: Some(vec!["/app/test-binary".to_string()]),
+                working_dir: "/".to_string(),
+                user: "nonroot:nonroot".to_string(),
+            },
+            rootfs: RootFs {
+                fs_type: "layers".to_string(),
+                diff_ids: vec![
+                    "sha256:base_layer_1".to_string(),
+                    "sha256:base_layer_2".to_string(),
+                    "sha256:app_layer".to_string(),
+                ],
+            },
+            history: vec![
+                History {
+                    created: "2023-01-01T00:00:00Z".to_string(),
+                    created_by: "base-image-builder".to_string(),
+                    comment: "Base layer 1".to_string(),
+                    empty_layer: false,
+                },
+                History {
+                    created: "2023-01-01T00:01:00Z".to_string(),
+                    created_by: "base-image-builder".to_string(),
+                    comment: "Base layer 2".to_string(),
+                    empty_layer: false,
+                },
+                History {
+                    created: "2023-01-01T00:02:00Z".to_string(),
+                    created_by: "krust".to_string(),
+                    comment: "Built with krust".to_string(),
+                    empty_layer: false,
+                },
+            ],
+        };
+
+        // Test that layered configs preserve base image properties
+        assert_eq!(config.rootfs.diff_ids.len(), 3);
+        assert_eq!(config.history.len(), 3);
+
+        // Verify diff_ids match expected order
+        assert_eq!(config.rootfs.diff_ids[0], "sha256:base_layer_1");
+        assert_eq!(config.rootfs.diff_ids[1], "sha256:base_layer_2");
+        assert_eq!(config.rootfs.diff_ids[2], "sha256:app_layer");
+
+        // Verify history is preserved and extended
+        assert_eq!(config.history[0].created_by, "base-image-builder");
+        assert_eq!(config.history[1].created_by, "base-image-builder");
+        assert_eq!(config.history[2].created_by, "krust");
+
+        // Verify base image environment is preserved
+        assert!(config
+            .config
+            .env
+            .contains(&"SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt".to_string()));
+        assert!(config.config.env.iter().any(|env| env.starts_with("PATH=")));
+    }
+}

src/registry/tests.rs

@@ -1,27 +0,0 @@
-#[cfg(test)]
-mod tests {
-    use super::super::*;
-
-    #[test]
-    fn test_parse_image_reference() {
-        let (registry, repo, tag) =
-            parse_image_reference("docker.io/library/hello-world:latest").unwrap();
-        assert_eq!(registry, "docker.io");
-        assert_eq!(repo, "library/hello-world");
-        assert_eq!(tag, "latest");
-    }
-
-    #[test]
-    fn test_parse_image_reference_no_tag() {
-        let (_, _, tag) = parse_image_reference("docker.io/library/hello-world").unwrap();
-        assert_eq!(tag, "latest");
-    }
-
-    #[test]
-    fn test_parse_image_reference_with_port() {
-        let (registry, repo, tag) = parse_image_reference("localhost:5000/myapp:v1.0").unwrap();
-        assert_eq!(registry, "localhost:5000");
-        assert_eq!(repo, "myapp");
-        assert_eq!(tag, "v1.0");
-    }
-}