code refactor

Reviewed-on: #26

crates/domain/tests/services/review_history_test.rs

@@ -0,0 +1,69 @@
+use chrono::{NaiveDate, NaiveDateTime, NaiveTime};
+use domain::models::{Review, ReviewHistory};
+use domain::services::review_history::{ReviewHistoryAnalyzer, Trend};
+use domain::testing::test_movie_with_year;
+use domain::value_objects::{MovieId, Rating, UserId};
+
+fn dt(year: i32, month: u32, day: u32) -> NaiveDateTime {
+    NaiveDateTime::new(
+        NaiveDate::from_ymd_opt(year, month, day).unwrap(),
+        NaiveTime::from_hms_opt(12, 0, 0).unwrap(),
+    )
+}
+
+fn review_with_rating(movie_id: &MovieId, rating: u8, watched_at: NaiveDateTime) -> Review {
+    let user_id = UserId::generate();
+    Review::new(
+        movie_id.clone(),
+        user_id,
+        Rating::new(rating).unwrap(),
+        None,
+        watched_at,
+        None,
+        false,
+    )
+    .unwrap()
+}
+
+#[test]
+fn neutral_when_empty() {
+    let movie = test_movie_with_year("Test", 2024);
+    let history = ReviewHistory::new(movie, vec![]);
+    let trend = ReviewHistoryAnalyzer::rating_trend(&history).unwrap();
+    assert_eq!(trend, Trend::Neutral);
+}
+
+#[test]
+fn neutral_when_single_review() {
+    let movie = test_movie_with_year("Test", 2024);
+    let r = review_with_rating(movie.id(), 4, dt(2024, 1, 1));
+    let history = ReviewHistory::new(movie, vec![r]);
+    let trend = ReviewHistoryAnalyzer::rating_trend(&history).unwrap();
+    assert_eq!(trend, Trend::Neutral);
+}
+
+#[test]
+fn improved_when_latest_above_average() {
+    let movie = test_movie_with_year("Test", 2024);
+    let viewings = vec![
+        review_with_rating(movie.id(), 2, dt(2024, 1, 1)),
+        review_with_rating(movie.id(), 3, dt(2024, 2, 1)),
+        review_with_rating(movie.id(), 5, dt(2024, 3, 1)),
+    ];
+    let history = ReviewHistory::new(movie, viewings);
+    let trend = ReviewHistoryAnalyzer::rating_trend(&history).unwrap();
+    assert_eq!(trend, Trend::Improved);
+}
+
+#[test]
+fn declined_when_latest_below_average() {
+    let movie = test_movie_with_year("Test", 2024);
+    let viewings = vec![
+        review_with_rating(movie.id(), 5, dt(2024, 1, 1)),
+        review_with_rating(movie.id(), 4, dt(2024, 2, 1)),
+        review_with_rating(movie.id(), 2, dt(2024, 3, 1)),
+    ];
+    let history = ReviewHistory::new(movie, viewings);
+    let trend = ReviewHistoryAnalyzer::rating_trend(&history).unwrap();
+    assert_eq!(trend, Trend::Declined);
+}