feat(tazjin/finito): Check in my old Rust state-machine library

I dug through my archives for this and found a version that, while
unfortunately not the latest implementation, is close enough to the
real thing to show off what Finito did.

This is a Postgres-backed state-machine library for complex
application logic. I wrote this originally for a work purpose in a
previous life, but have always wanted to apply it elsewhere, too.

git-subtree-dir: users/tazjin/finito
git-subtree-mainline: 0380841eb1
git-subtree-split: b748117225
Change-Id: I0de02d6258568447a14870f1a533812a67127763

users/tazjin/finito/finito-postgres/src/tests.rs

@@ -0,0 +1,47 @@
+use super::*;
+
+use finito_door::*;
+use postgres::{Connection, TlsMode};
+
+// TODO: read config from environment
+fn open_test_connection() -> Connection {
+    Connection::connect("postgres://finito:finito@localhost/finito", TlsMode::None)
+        .expect("Failed to connect to test database")
+}
+
+#[test]
+fn test_insert_machine() {
+    let conn = open_test_connection();
+    let initial = DoorState::Opened;
+    let door = insert_machine(&conn, initial).expect("Failed to insert door");
+    let result = get_machine(&conn, &door, false).expect("Failed to fetch door");
+
+    assert_eq!(result, DoorState::Opened, "Inserted door state should match");
+}
+
+#[test]
+fn test_advance() {
+    let conn = open_test_connection();
+
+    let initial = DoorState::Opened;
+    let events = vec![
+        DoorEvent::Close,
+        DoorEvent::Open,
+        DoorEvent::Close,
+        DoorEvent::Lock(1234),
+        DoorEvent::Unlock(1234),
+        DoorEvent::Lock(4567),
+        DoorEvent::Unlock(1234),
+    ];
+
+    let door = insert_machine(&conn, initial).expect("Failed to insert door");
+
+    for event in events {
+        advance(&conn, &door, event).expect("Failed to advance door FSM");
+    }
+
+    let result = get_machine(&conn, &door, false).expect("Failed to fetch door");
+    let expected = DoorState::Locked { code: 4567, attempts: 2 };
+
+    assert_eq!(result, expected, "Advanced door state should match");
+}