Validate when result of Item is un-sorted

KissMeme/KissDB.swift

@@ -126,6 +126,8 @@ public class KissDB: NSObject {
         }
     }
     
+    /// The result of `Item` is not sorted.
+    /// 
     public func select(into: ((Item)->Bool)?) throws {
         let obj = ItemCallbackObject(itemCallback: into)
         let userPtr = Unmanaged.passUnretained(obj).toOpaque()

KissMemeTests/KissMemeTests.swift

@@ -62,14 +62,23 @@ final class KissMemeTests: XCTestCase {
         try db.begin()
         print("DB count: \(db.count)")
         
-        var index = 0
+        var result = [String: String]()
         try db.select(into: { item in
-            XCTAssertTrue(item.key == "hello\(index)")
-            XCTAssertTrue(item.value == "world\(index)")
-            index += 1
+            result[item.key] = item.value
             return true
         })
         
+        for i in 0 ..< maxItems {
+            guard let value = result["hello\(i)"] else {
+                XCTAssertThrowsError("key not exist for hello\(i)")
+                continue
+            }
+            guard value == "world\(i)" else {
+                XCTAssertThrowsError("value not matched for hello\(i) \(value)")
+                continue
+            }
+        }
+        
         try db.rollback()
         let endTime = KissDB.appTime
         print("DB count: \(db.count) selectAll elapsed: \(endTime - startTime)")