diff --git a/Packages/vChewing_LangModelAssembly/Tests/LangModelAssemblyTests/LMCassetteTests.swift b/Packages/vChewing_LangModelAssembly/Tests/LangModelAssemblyTests/LMCassetteTests.swift
index 62908ef8..a7c1eee7 100644
--- a/Packages/vChewing_LangModelAssembly/Tests/LangModelAssemblyTests/LMCassetteTests.swift
+++ b/Packages/vChewing_LangModelAssembly/Tests/LangModelAssemblyTests/LMCassetteTests.swift
@@ -1,5 +1,4 @@
 //// (c) 2021 and onwards The vChewing Project (MIT-NTL License).
-// StringView Ranges extension by (c) 2022 and onwards Isaac Xen (MIT License).
 // ====================
 // This code is released under the MIT license (SPDX-License-Identifier: MIT)
 // ... with NTL restriction stating that:
@@ -49,8 +48,8 @@ final class LMCassetteTests: XCTestCase {
     XCTAssertFalse(lmCassette.quickDefMap.isEmpty)
     print(lmCassette.quickSetsFor(key: ",.") ?? "")
     XCTAssertEqual(lmCassette.keyNameMap.count, 41)
-    XCTAssertEqual(lmCassette.charDefMap.count, 29537)
-    XCTAssertEqual(lmCassette.charDefWildcardMap.count, 11973)
+    XCTAssertEqual(lmCassette.charDefMap.count, 29491)
+    XCTAssertEqual(lmCassette.charDefWildcardMap.count, 11946)
     XCTAssertEqual(lmCassette.octagramMap.count, 0)
     XCTAssertEqual(lmCassette.octagramDividedMap.count, 0)
     XCTAssertEqual(lmCassette.nameShort, "AR30")
diff --git a/Packages/vChewing_LangModelAssembly/Tests/LangModelAssemblyTests/LMUserOverrideTests.swift b/Packages/vChewing_LangModelAssembly/Tests/LangModelAssemblyTests/LMUserOverrideTests.swift
new file mode 100644
index 00000000..225d8079
--- /dev/null
+++ b/Packages/vChewing_LangModelAssembly/Tests/LangModelAssemblyTests/LMUserOverrideTests.swift
@@ -0,0 +1,106 @@
+//// (c) 2021 and onwards The vChewing Project (MIT-NTL License).
+// ====================
+// This code is released under the MIT license (SPDX-License-Identifier: MIT)
+// ... with NTL restriction stating that:
+// No trademark license is granted to use the trade names, trademarks, service
+// marks, or product names of Contributor, except as required to fulfill notice
+// requirements defined in MIT License.
+
+import Foundation
+import XCTest
+
+@testable import LangModelAssembly
+
+private let nowTimeStamp: Double = 114_514 * 10000
+private let capacity = 5
+private let halfLife: Double = 5400
+private let nullURL = URL(fileURLWithPath: "/dev/null")
+
+final class LMUserOverrideTests: XCTestCase {
+  private func observe(who uom: vChewingLM.LMUserOverride, key: String, candidate: String, timestamp stamp: Double) {
+    uom.doObservation(key: key, candidate: candidate, timestamp: stamp, forceHighScoreOverride: false, saveCallback: {})
+  }
+
+  func testUOM_1_BasicOps() throws {
+    let uom = vChewingLM.LMUserOverride(capacity: capacity, decayConstant: Double(halfLife), dataURL: nullURL)
+    let key = "((ㄍㄨㄥ-ㄙ,公司),(ㄉㄜ˙,的),ㄋㄧㄢˊ-ㄓㄨㄥ)"
+    let headReading = "ㄋㄧㄢˊ-ㄓㄨㄥ"
+    let expectedSuggestion = "年終"
+    observe(who: uom, key: key, candidate: expectedSuggestion, timestamp: nowTimeStamp)
+    var suggested = uom.getSuggestion(key: key, timestamp: nowTimeStamp, headReading: headReading)
+    XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", expectedSuggestion)
+    var i = 0
+    while !suggested.candidates.isEmpty {
+      suggested = uom.getSuggestion(key: key, timestamp: nowTimeStamp + (halfLife * Double(i)), headReading: headReading)
+      let suggestedCandidates = suggested.candidates
+      if suggestedCandidates.isEmpty { print(i) }
+      if i >= 21 {
+        XCTAssertNotEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", expectedSuggestion, i.description)
+        XCTAssert(suggested.candidates.isEmpty)
+      } else {
+        XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", expectedSuggestion, i.description)
+      }
+      i += 1
+    }
+  }
+
+  func testUOM_2_NewestAgainstRepeatedlyUsed() throws {
+    let uom = vChewingLM.LMUserOverride(capacity: capacity, decayConstant: Double(halfLife), dataURL: nullURL)
+    let key = "((ㄍㄨㄥ-ㄙ,公司),(ㄉㄜ˙,的),ㄋㄧㄢˊ-ㄓㄨㄥ)"
+    let headReading = "ㄋㄧㄢˊ-ㄓㄨㄥ"
+    let valRepeatedlyUsed = "年終" // 更常用
+    let valNewest = "年中" // 最近偶爾用了一次
+    let stamps: [Double] = [0, 0.5, 2, 2.5, 4, 4.5, 5.3].map { nowTimeStamp + halfLife * $0 }
+    stamps.forEach { stamp in
+      observe(who: uom, key: key, candidate: valRepeatedlyUsed, timestamp: stamp)
+    }
+    var suggested = uom.getSuggestion(key: key, timestamp: nowTimeStamp, headReading: headReading)
+    XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", valRepeatedlyUsed)
+    [6.0, 18.0, 23.0].forEach { i in
+      suggested = uom.getSuggestion(key: key, timestamp: nowTimeStamp + halfLife * Double(i), headReading: headReading)
+      XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", valRepeatedlyUsed, i.description)
+    }
+    // 試試看偶爾選了不常用的詞的話、是否會影響上文所生成的有一定強效的記憶。
+    observe(who: uom, key: key, candidate: valNewest, timestamp: nowTimeStamp + halfLife * 23.4)
+    suggested = uom.getSuggestion(key: key, timestamp: nowTimeStamp + halfLife * 23.6, headReading: headReading)
+    XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", valNewest)
+    suggested = uom.getSuggestion(key: key, timestamp: nowTimeStamp + halfLife * 26, headReading: headReading)
+    XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", valNewest)
+    suggested = uom.getSuggestion(key: key, timestamp: nowTimeStamp + halfLife * 50, headReading: headReading)
+    XCTAssertNotEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", valNewest)
+    XCTAssert(suggested.candidates.isEmpty)
+  }
+
+  func testUOM_3_LRUTable() throws {
+    let a = (key: "((ㄍㄨㄥ-ㄙ,公司),(ㄉㄜ˙,的),ㄋㄧㄢˊ-ㄓㄨㄥ)", value: "年終", head: "ㄋㄧㄢˊ-ㄓㄨㄥ")
+    let b = (key: "((ㄑㄧˋ-ㄧㄝˋ,企業),(ㄉㄜ˙,的),ㄐㄧㄤˇ-ㄐㄧㄣ)", value: "獎金", head: "ㄐㄧㄤˇ-ㄐㄧㄣ")
+    let c = (key: "((ㄒㄩㄝˊ-ㄕㄥ,學生),(ㄉㄜ˙,的),ㄈㄨˊ-ㄌㄧˋ)", value: "福利", head: "ㄈㄨˊ-ㄌㄧˋ")
+    let d = (key: "((ㄌㄟˊ-ㄉㄧㄢˋ-ㄐㄧㄤ-ㄐㄩㄣ,雷電將軍),(ㄉㄜ˙,的),ㄐㄧㄠˇ-ㄔㄡˋ)", value: "腳臭", head: "ㄐㄧㄠˇ-ㄔㄡˋ")
+    let uom = vChewingLM.LMUserOverride(capacity: 2, decayConstant: Double(halfLife), dataURL: nullURL)
+    observe(who: uom, key: a.key, candidate: a.value, timestamp: nowTimeStamp)
+    observe(who: uom, key: b.key, candidate: b.value, timestamp: nowTimeStamp + halfLife * 1)
+    observe(who: uom, key: c.key, candidate: c.value, timestamp: nowTimeStamp + halfLife * 2)
+    // C is in the list.
+    var suggested = uom.getSuggestion(key: c.key, timestamp: nowTimeStamp + halfLife * 3, headReading: c.head)
+    XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", c.value)
+    // B is in the list.
+    suggested = uom.getSuggestion(key: b.key, timestamp: nowTimeStamp + halfLife * 3.5, headReading: b.head)
+    XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", b.value)
+    // A is purged.
+    suggested = uom.getSuggestion(key: a.key, timestamp: nowTimeStamp + halfLife * 4, headReading: a.head)
+    XCTAssertNotEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", a.value)
+    XCTAssert(suggested.candidates.isEmpty)
+    // Observe a new pair (D).
+    observe(who: uom, key: d.key, candidate: d.value, timestamp: nowTimeStamp + halfLife * 4.5)
+    // D is in the list.
+    suggested = uom.getSuggestion(key: d.key, timestamp: nowTimeStamp + halfLife * 5, headReading: d.head)
+    XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", d.value)
+    // C is in the list.
+    suggested = uom.getSuggestion(key: c.key, timestamp: nowTimeStamp + halfLife * 5.5, headReading: c.head)
+    XCTAssertEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", c.value)
+    // B is purged.
+    suggested = uom.getSuggestion(key: b.key, timestamp: nowTimeStamp + halfLife * 6, headReading: b.head)
+    XCTAssertNotEqual(Set(suggested.candidates.map(\.1.value)).first ?? "", b.value)
+    XCTAssert(suggested.candidates.isEmpty)
+  }
+}