Add a failing test forr #514

Tests/GRDBTests/DatabaseRegionObservationTests.swift

@@ -152,4 +152,40 @@ class DatabaseRegionObservationTests: GRDBTestCase {
 
         XCTAssertEqual(count, 1)
     }
+
+    // Regression test
+    func testIssue514() throws {
+        let dbQueue = try makeDatabaseQueue()
+        try dbQueue.write { db in
+            try db.create(table: "gallery") { t in
+                t.column("id", .integer).primaryKey()
+                t.column("status", .integer)
+            }
+        }
+
+        struct Gallery: TableRecord { }
+        let observation = DatabaseRegionObservation(tracking: Gallery.select(Column("id")))
+
+        var notificationCount = 0
+        let observer = try observation.start(in: dbQueue) { _ in
+            notificationCount += 1
+        }
+
+        try withExtendedLifetime(observer) {
+            try dbQueue.write { db in
+                try db.execute(sql: "INSERT INTO gallery (id, status) VALUES (NULL, 0)")
+            }
+            XCTAssertEqual(notificationCount, 1)
+
+            try dbQueue.write { db in
+                try db.execute(sql: "UPDATE gallery SET status = 1")
+            }
+            XCTAssertEqual(notificationCount, 1) // status is not observed
+
+            try dbQueue.write { db in
+                try db.execute(sql: "DELETE FROM gallery")
+            }
+            XCTAssertEqual(notificationCount, 2)
+        }
+    }
 }