diff --git a/Cargo.lock b/Cargo.lock
index 2ce068c..168fa25 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -90,6 +90,7 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "async-trait",
+ "bytes",
  "domain",
  "thiserror",
  "tokio",
diff --git a/crates/application/Cargo.toml b/crates/application/Cargo.toml
index 1fb2d49..4fb737f 100644
--- a/crates/application/Cargo.toml
+++ b/crates/application/Cargo.toml
@@ -10,3 +10,4 @@ anyhow      = { workspace = true }
 thiserror   = { workspace = true }
 uuid        = { workspace = true }
 tokio       = { workspace = true }
+bytes       = { workspace = true }
diff --git a/crates/application/src/testing.rs b/crates/application/src/testing.rs
deleted file mode 100644
index 3c66fcc..0000000
--- a/crates/application/src/testing.rs
+++ /dev/null
@@ -1,85 +0,0 @@
-use std::collections::HashMap;
-use async_trait::async_trait;
-use tokio::sync::Mutex;
-use domain::{
-    entities::User,
-    errors::DomainError,
-    ports::{PasswordHasher, TokenIssuer, UserRepository},
-    value_objects::{Email, PasswordHash, SystemId},
-};
-
-pub struct InMemoryUserRepository {
-    users: Mutex<HashMap<String, User>>,
-}
-
-impl InMemoryUserRepository {
-    pub fn new() -> Self {
-        Self { users: Mutex::new(HashMap::new()) }
-    }
-
-    pub async fn all(&self) -> Vec<User> {
-        self.users.lock().await.values().cloned().collect()
-    }
-}
-
-impl Default for InMemoryUserRepository {
-    fn default() -> Self { Self::new() }
-}
-
-#[async_trait]
-impl UserRepository for InMemoryUserRepository {
-    async fn find_by_id(&self, id: &SystemId) -> Result<Option<User>, DomainError> {
-        Ok(self.users.lock().await.get(&id.to_string()).cloned())
-    }
-
-    async fn find_by_email(&self, email: &Email) -> Result<Option<User>, DomainError> {
-        Ok(self.users.lock().await.values()
-            .find(|u| u.email.as_str() == email.as_str())
-            .cloned())
-    }
-
-    async fn find_by_username(&self, username: &str) -> Result<Option<User>, DomainError> {
-        Ok(self.users.lock().await.values()
-            .find(|u| u.username == username)
-            .cloned())
-    }
-
-    async fn save(&self, user: &User) -> Result<(), DomainError> {
-        self.users.lock().await.insert(user.id.to_string(), user.clone());
-        Ok(())
-    }
-
-    async fn delete(&self, id: &SystemId) -> Result<(), DomainError> {
-        self.users.lock().await.remove(&id.to_string());
-        Ok(())
-    }
-}
-
-pub struct StubPasswordHasher;
-
-#[async_trait]
-impl PasswordHasher for StubPasswordHasher {
-    async fn hash(&self, password: &str) -> Result<PasswordHash, DomainError> {
-        Ok(PasswordHash::from_hash(format!("hashed:{password}")))
-    }
-    async fn verify(&self, password: &str, hash: &PasswordHash) -> Result<bool, DomainError> {
-        Ok(hash.as_str() == format!("hashed:{password}"))
-    }
-}
-
-pub struct StubTokenIssuer;
-
-#[async_trait]
-impl TokenIssuer for StubTokenIssuer {
-    async fn issue(&self, user_id: &SystemId, _role: &str) -> Result<String, DomainError> {
-        Ok(format!("token:{user_id}"))
-    }
-    async fn verify(&self, token: &str) -> Result<(SystemId, String), DomainError> {
-        let id_str = token.strip_prefix("token:").ok_or_else(|| {
-            DomainError::Unauthorized("Invalid stub token".to_string())
-        })?;
-        let uuid = uuid::Uuid::parse_str(id_str)
-            .map_err(|_| DomainError::Unauthorized("Bad UUID in stub token".to_string()))?;
-        Ok((SystemId::from_uuid(uuid), "user".to_string()))
-    }
-}
diff --git a/crates/application/src/testing/fakes.rs b/crates/application/src/testing/fakes.rs
new file mode 100644
index 0000000..57bd33f
--- /dev/null
+++ b/crates/application/src/testing/fakes.rs
@@ -0,0 +1,143 @@
+use std::collections::HashMap;
+use async_trait::async_trait;
+use bytes::Bytes;
+use tokio::sync::Mutex;
+use domain::{
+    errors::DomainError,
+    events::DomainEvent,
+    ports::{EventPublisher, FileStoragePort, FileEntry, PasswordHasher, TokenIssuer, SidecarWriterPort},
+    value_objects::{PasswordHash, StructuredData, SystemId},
+};
+
+// --- StubEventPublisher ---
+
+pub struct StubEventPublisher {
+    events: Mutex<Vec<DomainEvent>>,
+}
+
+impl StubEventPublisher {
+    pub fn new() -> Self {
+        Self { events: Mutex::new(Vec::new()) }
+    }
+
+    pub async fn published(&self) -> Vec<DomainEvent> {
+        self.events.lock().await.clone()
+    }
+}
+
+impl Default for StubEventPublisher {
+    fn default() -> Self { Self::new() }
+}
+
+#[async_trait]
+impl EventPublisher for StubEventPublisher {
+    async fn publish(&self, event: DomainEvent) -> Result<(), DomainError> {
+        self.events.lock().await.push(event);
+        Ok(())
+    }
+}
+
+// --- InMemoryFileStorage ---
+
+pub struct InMemoryFileStorage {
+    files: Mutex<HashMap<String, Bytes>>,
+}
+
+impl InMemoryFileStorage {
+    pub fn new() -> Self {
+        Self { files: Mutex::new(HashMap::new()) }
+    }
+}
+
+impl Default for InMemoryFileStorage {
+    fn default() -> Self { Self::new() }
+}
+
+#[async_trait]
+impl FileStoragePort for InMemoryFileStorage {
+    async fn store_file(&self, path: &str, data: Bytes) -> Result<(), DomainError> {
+        self.files.lock().await.insert(path.to_string(), data);
+        Ok(())
+    }
+
+    async fn read_file(&self, path: &str) -> Result<Bytes, DomainError> {
+        self.files.lock().await.get(path).cloned()
+            .ok_or_else(|| DomainError::NotFound(format!("File not found: {path}")))
+    }
+
+    async fn delete_file(&self, path: &str) -> Result<(), DomainError> {
+        self.files.lock().await.remove(path);
+        Ok(())
+    }
+
+    async fn list_directory(&self, path: &str) -> Result<Vec<FileEntry>, DomainError> {
+        let files = self.files.lock().await;
+        let prefix = if path.ends_with('/') { path.to_string() } else { format!("{path}/") };
+        Ok(files.keys()
+            .filter(|k| k.starts_with(&prefix))
+            .map(|k| FileEntry {
+                path: k.clone(),
+                size_bytes: files.get(k).map(|b| b.len() as u64).unwrap_or(0),
+                is_directory: false,
+            })
+            .collect())
+    }
+
+    async fn file_exists(&self, path: &str) -> Result<bool, DomainError> {
+        Ok(self.files.lock().await.contains_key(path))
+    }
+
+    async fn available_space(&self) -> Result<u64, DomainError> {
+        Ok(u64::MAX)
+    }
+}
+
+// --- StubSidecarWriter ---
+
+pub struct StubSidecarWriter;
+
+#[async_trait]
+impl SidecarWriterPort for StubSidecarWriter {
+    fn format_name(&self) -> &str { "stub" }
+
+    async fn write_sidecar(&self, _data: &StructuredData, _path: &str) -> Result<(), DomainError> {
+        Ok(())
+    }
+
+    async fn read_sidecar(&self, _path: &str) -> Result<StructuredData, DomainError> {
+        Ok(StructuredData::new())
+    }
+}
+
+// --- StubPasswordHasher ---
+
+pub struct StubPasswordHasher;
+
+#[async_trait]
+impl PasswordHasher for StubPasswordHasher {
+    async fn hash(&self, password: &str) -> Result<PasswordHash, DomainError> {
+        Ok(PasswordHash::from_hash(format!("hashed:{password}")))
+    }
+    async fn verify(&self, password: &str, hash: &PasswordHash) -> Result<bool, DomainError> {
+        Ok(hash.as_str() == format!("hashed:{password}"))
+    }
+}
+
+// --- StubTokenIssuer ---
+
+pub struct StubTokenIssuer;
+
+#[async_trait]
+impl TokenIssuer for StubTokenIssuer {
+    async fn issue(&self, user_id: &SystemId, _role: &str) -> Result<String, DomainError> {
+        Ok(format!("token:{user_id}"))
+    }
+    async fn verify(&self, token: &str) -> Result<(SystemId, String), DomainError> {
+        let id_str = token.strip_prefix("token:").ok_or_else(|| {
+            DomainError::Unauthorized("Invalid stub token".to_string())
+        })?;
+        let uuid = uuid::Uuid::parse_str(id_str)
+            .map_err(|_| DomainError::Unauthorized("Bad UUID in stub token".to_string()))?;
+        Ok((SystemId::from_uuid(uuid), "user".to_string()))
+    }
+}
diff --git a/crates/application/src/testing/mod.rs b/crates/application/src/testing/mod.rs
new file mode 100644
index 0000000..a846338
--- /dev/null
+++ b/crates/application/src/testing/mod.rs
@@ -0,0 +1,5 @@
+pub mod fakes;
+pub mod repositories;
+
+pub use fakes::*;
+pub use repositories::*;
diff --git a/crates/application/src/testing/repositories.rs b/crates/application/src/testing/repositories.rs
new file mode 100644
index 0000000..ea59c8e
--- /dev/null
+++ b/crates/application/src/testing/repositories.rs
@@ -0,0 +1,278 @@
+use std::collections::HashMap;
+use async_trait::async_trait;
+use tokio::sync::Mutex;
+use domain::{
+    entities::{Album, Asset, Group, Job, JobStatus, Role, User},
+    errors::DomainError,
+    ports::{
+        AlbumRepository, AssetRepository, GroupRepository,
+        JobRepository, RoleRepository, UserRepository,
+    },
+    value_objects::{Checksum, Email, SystemId},
+};
+
+// --- InMemoryUserRepository ---
+
+pub struct InMemoryUserRepository {
+    users: Mutex<HashMap<String, User>>,
+}
+
+impl InMemoryUserRepository {
+    pub fn new() -> Self {
+        Self { users: Mutex::new(HashMap::new()) }
+    }
+
+    pub async fn all(&self) -> Vec<User> {
+        self.users.lock().await.values().cloned().collect()
+    }
+}
+
+impl Default for InMemoryUserRepository {
+    fn default() -> Self { Self::new() }
+}
+
+#[async_trait]
+impl UserRepository for InMemoryUserRepository {
+    async fn find_by_id(&self, id: &SystemId) -> Result<Option<User>, DomainError> {
+        Ok(self.users.lock().await.get(&id.to_string()).cloned())
+    }
+
+    async fn find_by_email(&self, email: &Email) -> Result<Option<User>, DomainError> {
+        Ok(self.users.lock().await.values()
+            .find(|u| u.email.as_str() == email.as_str())
+            .cloned())
+    }
+
+    async fn find_by_username(&self, username: &str) -> Result<Option<User>, DomainError> {
+        Ok(self.users.lock().await.values()
+            .find(|u| u.username == username)
+            .cloned())
+    }
+
+    async fn save(&self, user: &User) -> Result<(), DomainError> {
+        self.users.lock().await.insert(user.id.to_string(), user.clone());
+        Ok(())
+    }
+
+    async fn delete(&self, id: &SystemId) -> Result<(), DomainError> {
+        self.users.lock().await.remove(&id.to_string());
+        Ok(())
+    }
+}
+
+// --- InMemoryAssetRepository ---
+
+pub struct InMemoryAssetRepository {
+    data: Mutex<HashMap<String, Asset>>,
+}
+
+impl InMemoryAssetRepository {
+    pub fn new() -> Self {
+        Self { data: Mutex::new(HashMap::new()) }
+    }
+}
+
+impl Default for InMemoryAssetRepository {
+    fn default() -> Self { Self::new() }
+}
+
+#[async_trait]
+impl AssetRepository for InMemoryAssetRepository {
+    async fn find_by_id(&self, id: &SystemId) -> Result<Option<Asset>, DomainError> {
+        Ok(self.data.lock().await.get(&id.to_string()).cloned())
+    }
+
+    async fn find_by_checksum(&self, checksum: &Checksum) -> Result<Vec<Asset>, DomainError> {
+        Ok(self.data.lock().await.values()
+            .filter(|a| &a.source_reference.checksum == checksum)
+            .cloned()
+            .collect())
+    }
+
+    async fn find_by_owner(&self, owner_id: &SystemId, limit: u32, offset: u32) -> Result<Vec<Asset>, DomainError> {
+        let all: Vec<Asset> = self.data.lock().await.values()
+            .filter(|a| &a.owner_user_id == owner_id)
+            .cloned()
+            .collect();
+        Ok(all.into_iter().skip(offset as usize).take(limit as usize).collect())
+    }
+
+    async fn save(&self, asset: &Asset) -> Result<(), DomainError> {
+        self.data.lock().await.insert(asset.asset_id.to_string(), asset.clone());
+        Ok(())
+    }
+
+    async fn delete(&self, id: &SystemId) -> Result<(), DomainError> {
+        self.data.lock().await.remove(&id.to_string());
+        Ok(())
+    }
+}
+
+// --- InMemoryAlbumRepository ---
+
+pub struct InMemoryAlbumRepository {
+    data: Mutex<HashMap<String, Album>>,
+}
+
+impl InMemoryAlbumRepository {
+    pub fn new() -> Self {
+        Self { data: Mutex::new(HashMap::new()) }
+    }
+}
+
+impl Default for InMemoryAlbumRepository {
+    fn default() -> Self { Self::new() }
+}
+
+#[async_trait]
+impl AlbumRepository for InMemoryAlbumRepository {
+    async fn find_by_id(&self, id: &SystemId) -> Result<Option<Album>, DomainError> {
+        Ok(self.data.lock().await.get(&id.to_string()).cloned())
+    }
+
+    async fn find_by_creator(&self, creator_id: &SystemId) -> Result<Vec<Album>, DomainError> {
+        Ok(self.data.lock().await.values()
+            .filter(|a| &a.creator_user_id == creator_id)
+            .cloned()
+            .collect())
+    }
+
+    async fn save(&self, album: &Album) -> Result<(), DomainError> {
+        self.data.lock().await.insert(album.album_id.to_string(), album.clone());
+        Ok(())
+    }
+
+    async fn delete(&self, id: &SystemId) -> Result<(), DomainError> {
+        self.data.lock().await.remove(&id.to_string());
+        Ok(())
+    }
+}
+
+// --- InMemoryJobRepository ---
+
+pub struct InMemoryJobRepository {
+    data: Mutex<HashMap<String, Job>>,
+}
+
+impl InMemoryJobRepository {
+    pub fn new() -> Self {
+        Self { data: Mutex::new(HashMap::new()) }
+    }
+}
+
+impl Default for InMemoryJobRepository {
+    fn default() -> Self { Self::new() }
+}
+
+#[async_trait]
+impl JobRepository for InMemoryJobRepository {
+    async fn find_by_id(&self, id: &SystemId) -> Result<Option<Job>, DomainError> {
+        Ok(self.data.lock().await.get(&id.to_string()).cloned())
+    }
+
+    async fn find_next_queued(&self) -> Result<Option<Job>, DomainError> {
+        let data = self.data.lock().await;
+        Ok(data.values()
+            .filter(|j| j.status == JobStatus::Queued)
+            .max_by_key(|j| j.priority)
+            .cloned())
+    }
+
+    async fn find_by_batch(&self, batch_id: &SystemId) -> Result<Vec<Job>, DomainError> {
+        Ok(self.data.lock().await.values()
+            .filter(|j| j.batch_id.as_ref() == Some(batch_id))
+            .cloned()
+            .collect())
+    }
+
+    async fn save(&self, job: &Job) -> Result<(), DomainError> {
+        self.data.lock().await.insert(job.job_id.to_string(), job.clone());
+        Ok(())
+    }
+}
+
+// --- InMemoryRoleRepository ---
+
+pub struct InMemoryRoleRepository {
+    data: Mutex<HashMap<String, Role>>,
+}
+
+impl InMemoryRoleRepository {
+    pub fn new() -> Self {
+        Self { data: Mutex::new(HashMap::new()) }
+    }
+}
+
+impl Default for InMemoryRoleRepository {
+    fn default() -> Self { Self::new() }
+}
+
+#[async_trait]
+impl RoleRepository for InMemoryRoleRepository {
+    async fn find_by_id(&self, id: &SystemId) -> Result<Option<Role>, DomainError> {
+        Ok(self.data.lock().await.get(&id.to_string()).cloned())
+    }
+
+    async fn find_by_name(&self, name: &str) -> Result<Option<Role>, DomainError> {
+        Ok(self.data.lock().await.values()
+            .find(|r| r.name == name)
+            .cloned())
+    }
+
+    async fn find_defaults(&self) -> Result<Vec<Role>, DomainError> {
+        Ok(self.data.lock().await.values()
+            .filter(|r| r.is_system_default)
+            .cloned()
+            .collect())
+    }
+
+    async fn save(&self, role: &Role) -> Result<(), DomainError> {
+        self.data.lock().await.insert(role.role_id.to_string(), role.clone());
+        Ok(())
+    }
+
+    async fn delete(&self, id: &SystemId) -> Result<(), DomainError> {
+        self.data.lock().await.remove(&id.to_string());
+        Ok(())
+    }
+}
+
+// --- InMemoryGroupRepository ---
+
+pub struct InMemoryGroupRepository {
+    data: Mutex<HashMap<String, Group>>,
+}
+
+impl InMemoryGroupRepository {
+    pub fn new() -> Self {
+        Self { data: Mutex::new(HashMap::new()) }
+    }
+}
+
+impl Default for InMemoryGroupRepository {
+    fn default() -> Self { Self::new() }
+}
+
+#[async_trait]
+impl GroupRepository for InMemoryGroupRepository {
+    async fn find_by_id(&self, id: &SystemId) -> Result<Option<Group>, DomainError> {
+        Ok(self.data.lock().await.get(&id.to_string()).cloned())
+    }
+
+    async fn find_by_user(&self, user_id: &SystemId) -> Result<Vec<Group>, DomainError> {
+        Ok(self.data.lock().await.values()
+            .filter(|g| g.is_member(user_id))
+            .cloned()
+            .collect())
+    }
+
+    async fn save(&self, group: &Group) -> Result<(), DomainError> {
+        self.data.lock().await.insert(group.group_id.to_string(), group.clone());
+        Ok(())
+    }
+
+    async fn delete(&self, id: &SystemId) -> Result<(), DomainError> {
+        self.data.lock().await.remove(&id.to_string());
+        Ok(())
+    }
+}