test(application): fill unit test gaps — api_keys, profile, auth, thoughts, social

crates/application/src/use_cases/auth.rs

@@ -124,4 +124,19 @@ mod tests {
         assert_eq!(events.len(), 1);
         assert!(matches!(events[0], DomainEvent::UserRegistered { .. }));
     }
+
+    #[tokio::test]
+    async fn login_fails_for_nonexistent_user() {
+        let store = TestStore::default();
+        let err = login(&store, &FakeHasher, &FakeAuth, LoginInput { email: "ghost@ex.com".into(), password: "pass".into() }).await.unwrap_err();
+        assert!(matches!(err, DomainError::Unauthorized));
+    }
+
+    #[tokio::test]
+    async fn register_rejects_duplicate_email() {
+        let store = TestStore::default();
+        register(&store, &FakeHasher, &FakeAuth, &NoOpEventPublisher, input()).await.unwrap();
+        let err = register(&store, &FakeHasher, &FakeAuth, &NoOpEventPublisher, RegisterInput { username: "alice2".into(), email: "alice@ex.com".into(), password: "pass2".into() }).await.unwrap_err();
+        assert!(matches!(err, DomainError::Conflict(_)));
+    }
 }