feat(domain): add Message constructor, accessors, and builder

crates/domain/src/message/tests.rs

@@ -0,0 +1,86 @@
+use super::*;
+use types::bounded::CapSlot;
+
+fn slot(n: u8) -> CapSlot {
+    CapSlot::new(n).unwrap()
+}
+
+// --- Construction ---
+
+#[test]
+fn empty_message_has_zeroed_words_and_no_caps() {
+    let msg = Message::empty();
+    assert_eq!(msg.words(), &[0; MAX_MESSAGE_WORDS]);
+    for i in 0..MAX_CAP_TRANSFERS {
+        assert!(msg.cap(i).is_none());
+    }
+}
+
+#[test]
+fn from_words_sets_words_and_no_caps() {
+    let msg = Message::from_words([10, 20, 30, 40]);
+    assert_eq!(msg.word(0), 10);
+    assert_eq!(msg.word(1), 20);
+    assert_eq!(msg.word(2), 30);
+    assert_eq!(msg.word(3), 40);
+    assert!(msg.cap(0).is_none());
+}
+
+// --- Accessors ---
+
+#[test]
+fn words_returns_full_array() {
+    let msg = Message::from_words([1, 2, 3, 4]);
+    assert_eq!(msg.words(), &[1, 2, 3, 4]);
+}
+
+#[test]
+fn caps_returns_full_array() {
+    let msg = Message::empty();
+    assert_eq!(msg.caps(), &[None; MAX_CAP_TRANSFERS]);
+}
+
+// --- Builder ---
+
+#[test]
+fn builder_sets_individual_words() {
+    let msg = Message::builder()
+        .word(0, 42)
+        .word(2, 99)
+        .build();
+    assert_eq!(msg.word(0), 42);
+    assert_eq!(msg.word(1), 0);
+    assert_eq!(msg.word(2), 99);
+    assert_eq!(msg.word(3), 0);
+}
+
+#[test]
+fn builder_sets_caps() {
+    let msg = Message::builder()
+        .cap(0, slot(5))
+        .cap(1, slot(10))
+        .build();
+    assert_eq!(msg.cap(0), Some(slot(5)));
+    assert_eq!(msg.cap(1), Some(slot(10)));
+    assert!(msg.cap(2).is_none());
+}
+
+#[test]
+fn builder_sets_words_and_caps_together() {
+    let msg = Message::builder()
+        .word(0, 100)
+        .word(1, 200)
+        .cap(0, slot(3))
+        .build();
+    assert_eq!(msg.word(0), 100);
+    assert_eq!(msg.word(1), 200);
+    assert_eq!(msg.cap(0), Some(slot(3)));
+}
+
+#[test]
+fn builder_with_all_words() {
+    let msg = Message::builder()
+        .words([11, 22, 33, 44])
+        .build();
+    assert_eq!(msg.words(), &[11, 22, 33, 44]);
+}