add 400+ unit tests for domain and application layers

Extract ReviewLogger trait to decouple import/integrations
from diary::log_review (cross-module coupling smell).

Add in-memory fakes for all repository ports, enabling
isolated testing of every use case module without a database.

Coverage: domain+application 22% → 80%, 427 tests.

crates/application/src/diary/tests/review_logger.rs

@@ -0,0 +1,310 @@
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use chrono::Utc;
+use domain::{
+    errors::DomainError,
+    models::Movie,
+    models::WatchlistEntry,
+    ports::{MetadataClient, MetadataSearchCriteria, MovieRepository, WatchlistRepository},
+    testing::{
+        FakeMetadataClient, InMemoryMovieRepository, InMemoryReviewRepository,
+        InMemoryWatchlistRepository, NoopEventPublisher,
+    },
+    value_objects::{ExternalMetadataId, MovieId, MovieTitle, PosterUrl, ReleaseYear, UserId},
+};
+use uuid::Uuid;
+
+use crate::diary::commands::{LogReviewCommand, MovieInput};
+use crate::diary::review_logger::DefaultReviewLogger;
+use crate::ports::ReviewLogger;
+
+fn make_logger(
+    movies: &Arc<InMemoryMovieRepository>,
+    reviews: &Arc<InMemoryReviewRepository>,
+    watchlist: &Arc<InMemoryWatchlistRepository>,
+    events: &Arc<NoopEventPublisher>,
+) -> DefaultReviewLogger {
+    DefaultReviewLogger::new(
+        Arc::clone(movies) as _,
+        Arc::clone(reviews) as _,
+        Arc::clone(watchlist) as _,
+        Arc::new(FakeMetadataClient) as _,
+        Arc::clone(events) as _,
+    )
+}
+
+#[tokio::test]
+async fn logs_review_with_manual_movie() {
+    let movies = InMemoryMovieRepository::new();
+    let reviews = InMemoryReviewRepository::new();
+    let watchlist = InMemoryWatchlistRepository::new();
+    let events = NoopEventPublisher::new();
+    let logger = make_logger(&movies, &reviews, &watchlist, &events);
+
+    let uid = Uuid::new_v4();
+    let cmd = LogReviewCommand {
+        user_id: uid,
+        input: MovieInput {
+            movie_id: None,
+            external_metadata_id: None,
+            manual_title: Some("Test Film".into()),
+            manual_release_year: Some(2024),
+            manual_director: None,
+        },
+        rating: 4,
+        comment: None,
+        watched_at: Utc::now().naive_utc(),
+    };
+
+    logger.log_review(cmd).await.unwrap();
+
+    assert_eq!(movies.count(), 1);
+    assert_eq!(reviews.count(), 1);
+}
+
+#[tokio::test]
+async fn removes_from_watchlist_on_review() {
+    let movies = InMemoryMovieRepository::new();
+    let reviews = InMemoryReviewRepository::new();
+    let watchlist = InMemoryWatchlistRepository::new();
+    let events = NoopEventPublisher::new();
+    let logger = make_logger(&movies, &reviews, &watchlist, &events);
+
+    let uid = Uuid::new_v4();
+    let user_id = UserId::from_uuid(uid);
+
+    // Create and store movie
+    let movie = Movie::new(
+        None,
+        MovieTitle::new("Watchlisted Film".into()).unwrap(),
+        ReleaseYear::new(2024).unwrap(),
+        None,
+        None,
+    );
+    let movie_id = movie.id().value();
+    movies.upsert_movie(&movie).await.unwrap();
+
+    // Add to watchlist
+    let entry = WatchlistEntry::new(user_id.clone(), MovieId::from_uuid(movie_id));
+    watchlist.add(&entry).await.unwrap();
+    assert_eq!(watchlist.count(), 1);
+
+    // Log review for same movie
+    let cmd = LogReviewCommand {
+        user_id: uid,
+        input: MovieInput {
+            movie_id: Some(movie_id),
+            external_metadata_id: None,
+            manual_title: None,
+            manual_release_year: None,
+            manual_director: None,
+        },
+        rating: 5,
+        comment: None,
+        watched_at: Utc::now().naive_utc(),
+    };
+
+    logger.log_review(cmd).await.unwrap();
+
+    assert_eq!(watchlist.count(), 0);
+}
+
+#[tokio::test]
+async fn logs_review_with_existing_movie_by_id() {
+    let movies = InMemoryMovieRepository::new();
+    let reviews = InMemoryReviewRepository::new();
+    let watchlist = InMemoryWatchlistRepository::new();
+    let events = NoopEventPublisher::new();
+    let logger = make_logger(&movies, &reviews, &watchlist, &events);
+
+    let movie = Movie::new(
+        None,
+        MovieTitle::new("Existing Film".into()).unwrap(),
+        ReleaseYear::new(2020).unwrap(),
+        None,
+        None,
+    );
+    let movie_uuid = movie.id().value();
+    movies.upsert_movie(&movie).await.unwrap();
+
+    let cmd = LogReviewCommand {
+        user_id: Uuid::new_v4(),
+        input: MovieInput {
+            movie_id: Some(movie_uuid),
+            external_metadata_id: None,
+            manual_title: None,
+            manual_release_year: None,
+            manual_director: None,
+        },
+        rating: 3,
+        comment: None,
+        watched_at: Utc::now().naive_utc(),
+    };
+
+    logger.log_review(cmd).await.unwrap();
+
+    assert_eq!(movies.count(), 1);
+    assert_eq!(reviews.count(), 1);
+}
+
+#[tokio::test]
+async fn existing_movie_not_found_returns_error() {
+    let movies = InMemoryMovieRepository::new();
+    let reviews = InMemoryReviewRepository::new();
+    let watchlist = InMemoryWatchlistRepository::new();
+    let events = NoopEventPublisher::new();
+    let logger = make_logger(&movies, &reviews, &watchlist, &events);
+
+    let cmd = LogReviewCommand {
+        user_id: Uuid::new_v4(),
+        input: MovieInput {
+            movie_id: Some(Uuid::new_v4()),
+            external_metadata_id: None,
+            manual_title: None,
+            manual_release_year: None,
+            manual_director: None,
+        },
+        rating: 4,
+        comment: None,
+        watched_at: Utc::now().naive_utc(),
+    };
+
+    assert!(logger.log_review(cmd).await.is_err());
+}
+
+#[tokio::test]
+async fn invalid_rating_returns_error() {
+    let movies = InMemoryMovieRepository::new();
+    let reviews = InMemoryReviewRepository::new();
+    let watchlist = InMemoryWatchlistRepository::new();
+    let events = NoopEventPublisher::new();
+    let logger = make_logger(&movies, &reviews, &watchlist, &events);
+
+    let cmd = LogReviewCommand {
+        user_id: Uuid::new_v4(),
+        input: MovieInput {
+            movie_id: None,
+            external_metadata_id: None,
+            manual_title: Some("Film".into()),
+            manual_release_year: Some(2024),
+            manual_director: None,
+        },
+        rating: 6,
+        comment: None,
+        watched_at: Utc::now().naive_utc(),
+    };
+
+    let result = logger.log_review(cmd).await;
+    assert!(result.is_err());
+    // No repo calls should have happened
+    assert_eq!(movies.count(), 0);
+    assert_eq!(reviews.count(), 0);
+}
+
+#[tokio::test]
+async fn watchlist_not_present_does_not_publish_removed() {
+    let movies = InMemoryMovieRepository::new();
+    let reviews = InMemoryReviewRepository::new();
+    let watchlist = InMemoryWatchlistRepository::new();
+    let events = NoopEventPublisher::new();
+    let logger = make_logger(&movies, &reviews, &watchlist, &events);
+
+    let cmd = LogReviewCommand {
+        user_id: Uuid::new_v4(),
+        input: MovieInput {
+            movie_id: None,
+            external_metadata_id: None,
+            manual_title: Some("No Watchlist Film".into()),
+            manual_release_year: Some(2024),
+            manual_director: None,
+        },
+        rating: 4,
+        comment: None,
+        watched_at: Utc::now().naive_utc(),
+    };
+
+    logger.log_review(cmd).await.unwrap();
+
+    let published = events.published();
+    assert!(
+        !published
+            .iter()
+            .any(|e| matches!(e, domain::events::DomainEvent::WatchlistEntryRemoved { .. })),
+        "should not publish WatchlistEntryRemoved when not on watchlist"
+    );
+}
+
+/// A metadata client that returns a movie with an external_metadata_id,
+/// triggering the MovieDiscovered event path.
+struct MetadataClientWithExternalId;
+
+#[async_trait]
+impl MetadataClient for MetadataClientWithExternalId {
+    async fn fetch_movie_metadata(
+        &self,
+        _criteria: &MetadataSearchCriteria,
+    ) -> Result<Movie, DomainError> {
+        Ok(Movie::new(
+            Some(ExternalMetadataId::new("tmdb:99999".into()).unwrap()),
+            MovieTitle::new("Discovered Film".into()).unwrap(),
+            ReleaseYear::new(2024).unwrap(),
+            None,
+            None,
+        ))
+    }
+
+    async fn get_poster_url(
+        &self,
+        _external_metadata_id: &ExternalMetadataId,
+    ) -> Result<Option<PosterUrl>, DomainError> {
+        Ok(None)
+    }
+}
+
+#[tokio::test]
+async fn publishes_movie_discovered_for_new_movie_with_external_id() {
+    let movies = InMemoryMovieRepository::new();
+    let reviews = InMemoryReviewRepository::new();
+    let watchlist = InMemoryWatchlistRepository::new();
+    let events = NoopEventPublisher::new();
+
+    let logger = DefaultReviewLogger::new(
+        Arc::clone(&movies) as _,
+        Arc::clone(&reviews) as _,
+        Arc::clone(&watchlist) as _,
+        Arc::new(MetadataClientWithExternalId) as _,
+        Arc::clone(&events) as _,
+    );
+
+    let cmd = LogReviewCommand {
+        user_id: Uuid::new_v4(),
+        input: MovieInput {
+            movie_id: None,
+            external_metadata_id: None,
+            manual_title: Some("Discovered Film".into()),
+            manual_release_year: Some(2024),
+            manual_director: None,
+        },
+        rating: 5,
+        comment: None,
+        watched_at: Utc::now().naive_utc(),
+    };
+
+    logger.log_review(cmd).await.unwrap();
+
+    let published = events.published();
+    assert!(
+        published
+            .iter()
+            .any(|e| matches!(e, domain::events::DomainEvent::MovieDiscovered { .. })),
+        "should publish MovieDiscovered for new movie with external_metadata_id"
+    );
+    assert!(
+        published.iter().any(|e| matches!(
+            e,
+            domain::events::DomainEvent::MovieEnrichmentRequested { .. }
+        )),
+        "should publish MovieEnrichmentRequested"
+    );
+}