标签：prot idg string pre equals 第三方 order 也会 电商
代码可测试性：
针对代码编写单元测试的难易程度。对于一段代码，如果很难为其编写单元测试，或者单元测试写起来很费劲，需要依靠单元测试框架中很高级的特性，那往往就意味着代码设计得不够合理，代码的可测试性不好
Transaction 是经过我抽象简化之后的一个电商系统的交易类，用来记录每笔订单交易的情况。Transaction 类中的 execute() 函数负责执行转账操作，将钱从买家的钱包转到卖家的钱包中。真正的转账操作是通过调用 WalletRpcService RPC 服务来完成的。除此之外，代码中还涉及一个分布式锁 DistributedLock 单例类，用来避免 Transaction 并发执行，导致用户的钱被重复转出。
public class Transaction {
private String id;
private Long buyerId;
private Long sellerId;
private Long productId;
private String orderId;
private Long createTimestamp;
private Double amount;
private STATUS status;
private String walletTransactionId;
// ...get() methods...
public Transaction(String preAssignedId, Long buyerId, Long sellerId, Long productId, String orderId) {
if (preAssignedId != null && !preAssignedId.isEmpty()) {
this.id = preAssignedId;
} else {
this.id = IdGenerator.generateTransactionId();
}
if (!this.id.startWith("t_")) {
this.id = "t_" + preAssignedId;
}
this.buyerId = buyerId;
this.sellerId = sellerId;
this.productId = productId;
this.orderId = orderId;
this.status = STATUS.TO_BE_EXECUTD;
this.createTimestamp = System.currentTimestamp();
}
public boolean execute() throws InvalidTransactionException {
if ((buyerId == null || (sellerId == null || amount < 0.0) {
throw new InvalidTransactionException(...);
}
if (status == STATUS.EXECUTED) return true;
boolean isLocked = false;
try {
isLocked = RedisDistributedLock.getSingletonIntance().lockTransction(id);
if (!isLocked) {
return false; // 锁定未成功，返回false，job兜底执行
}
if (status == STATUS.EXECUTED) return true; // double check
long executionInvokedTimestamp = System.currentTimestamp();
if (executionInvokedTimestamp - createdTimestap > 14days) {
this.status = STATUS.EXPIRED;
return false;
}
WalletRpcService walletRpcService = new WalletRpcService();
String walletTransactionId = walletRpcService.moveMoney(id, buyerId, sellerId, amount);
if (walletTransactionId != null) {
this.walletTransactionId = walletTransactionId;
this.status = STATUS.EXECUTED;
return true;
} else {
this.status = STATUS.FAILED;
return false;
}
} finally {
if (isLocked) {
RedisDistributedLock.getSingletonIntance().unlockTransction(id);
}
}
}
}
public void testExecute() {
Long buyerId = 123L;
Long sellerId = 234L;
Long productId = 345L;
Long orderId = 456L;
Transction transaction = new Transaction(null, buyerId, sellerId, productId, orderId);
boolean executedResult = transaction.execute();
assertTrue(executedResult);
}
问题
execute() 函数的执行依赖两个外部的服务，一个是 RedisDistributedLock，一个 WalletRpcService。这就导致上面的单元测试代码存在下面几个问题。
解决WalletRpcService mock的问题
继承 WalletRpcService 类，并且重写其中的 moveMoney() 函数的方式来实现 mock。具体的代码实现如下所示。通过 mock 的方式，可以让 moveMoney() 返回任意我们想要的数据，完全在我们的控制范围内，并且不需要真正进行网络通信
public class MockWalletRpcServiceOne extends WalletRpcService {
public String moveMoney(Long id, Long fromUserId, Long toUserId, Double amount) {
return "123bac";
}
}
public class MockWalletRpcServiceTwo extends WalletRpcService {
public String moveMoney(Long id, Long fromUserId, Long toUserId, Double amount) {
return null;
}
}
重构使WalletRpcService 可动态配置，增强 execute() 方法的可测试性
public class Transaction {
//...
// 添加一个成员变量及其set方法
private WalletRpcService walletRpcService;
public void setWalletRpcService(WalletRpcService walletRpcService) {
this.walletRpcService = walletRpcService;
}
// ...
public boolean execute() {
// ...
// 删除下面这一行代码
// WalletRpcService walletRpcService = new WalletRpcService();
// ...
}
}
测试实现
public void testExecute() {
Long buyerId = 123L;
Long sellerId = 234L;
Long productId = 345L;
Long orderId = 456L;
Transction transaction = new Transaction(null, buyerId, sellerId, productId, orderId);
// 使用mock对象来替代真正的RPC服务
transaction.setWalletRpcService(new MockWalletRpcServiceOne()):
boolean executedResult = transaction.execute();
assertTrue(executedResult);
assertEquals(STATUS.EXECUTED, transaction.getStatus());
}
解决RedisDistributedLock的替换和mock问题
RedisDistributedLock 是一个单例类。单例相当于一个全局变量，无法 mock（无法继承和重写方法），也无法通过依赖注入的方式来替换，且可能不是本方维护的类。
可以对 transaction 上锁这部分逻辑重新封装一下：
public class TransactionLock {
public boolean lock(String id) {
return RedisDistributedLock.getSingletonIntance().lockTransction(id);
}
public void unlock() {
RedisDistributedLock.getSingletonIntance().unlockTransction(id);
}
}
public class Transaction {
//...
private TransactionLock lock;
public void setTransactionLock(TransactionLock lock) {
this.lock = lock;
}
public boolean execute() {
//...
try {
isLocked = lock.lock();
//...
} finally {
if (isLocked) {
lock.unlock();
}
}
//...
}
}
测试实现
public void testExecute() {
Long buyerId = 123L;
Long sellerId = 234L;
Long productId = 345L;
Long orderId = 456L;
TransactionLock mockLock = new TransactionLock() {
public boolean lock(String id) {
return true;
}
public void unlock() {}
};
Transction transaction = new Transaction(null, buyerId, sellerId, productId, orderId);
transaction.setWalletRpcService(new MockWalletRpcServiceOne());
transaction.setTransactionLock(mockLock);
boolean executedResult = transaction.execute();
assertTrue(executedResult);
assertEquals(STATUS.EXECUTED, transaction.getStatus());
}
测试用例 3：交易已过期（createTimestamp 超过 14 天），交易状态设置为 EXPIRED，返回 false。上代码：
public void testExecute_with_TransactionIsExpired() {
Long buyerId = 123L;
Long sellerId = 234L;
Long productId = 345L;
Long orderId = 456L;
Transction transaction = new Transaction(null, buyerId, sellerId, productId, orderId);
transaction.setCreatedTimestamp(System.currentTimestamp() - 14days);
boolean actualResult = transaction.execute();
assertFalse(actualResult);
assertEquals(STATUS.EXPIRED, transaction.getStatus());
}
问题
如果在 Transaction 类中，并没有暴露修改 createdTimestamp 成员变量的 set 方法，上述代码是有问题的也不能随便给类添加setCreatedTimestamp方法，违反封装性：createTimestamp 是在交易生成时（也就是构造函数中）自动获取的系统时间，本来就不应该人为地轻易修改
解决问题
处理方式是将这种未决行为逻辑重新封装。
重构
针对 Transaction 类，只需要将交易是否过期的逻辑，封装到 isExpired() 函数中即可，具体的代码实现如下所示：
public class Transaction {
protected boolean isExpired() {
long executionInvokedTimestamp = System.currentTimestamp();
return executionInvokedTimestamp - createdTimestamp > 14days;
}
public boolean execute() throws InvalidTransactionException {
//...
if (isExpired()) {
this.status = STATUS.EXPIRED;
return false;
}
//...
}
}
测试实现
public void testExecute_with_TransactionIsExpired() {
Long buyerId = 123L;
Long sellerId = 234L;
Long productId = 345L;
Long orderId = 456L;
Transction transaction = new Transaction(null, buyerId, sellerId, productId, orderId) {
protected boolean isExpired() {
return true;
}
};
boolean actualResult = transaction.execute();
assertFalse(actualResult);
assertEquals(STATUS.EXPIRED, transaction.getStatus());
}
Transaction 类的构造函数的设计还有点不妥：交易 id 的赋值逻辑稍微复杂。最好也要测试一下，以保证这部分逻辑的正确性
public void testExecute_with_TransactionIsExpired() {
Long buyerId = 123L;
Long sellerId = 234L;
Long productId = 345L;
Long orderId = 456L;
Transction transaction = new Transaction(null, buyerId, sellerId, productId, orderId) {
protected boolean isExpired() {
return true;
}
};
boolean actualResult = transaction.execute();
assertFalse(actualResult);
assertEquals(STATUS.EXPIRED, transaction.getStatus());
}
重构一下，这样在测试代码中就可以通过重写fillTransactionId来mock测试
public Transaction(String preAssignedId, Long buyerId, Long sellerId, Long productId, String orderId) {
//...
fillTransactionId(preAssignId);
//...
}
protected void fillTransactionId(String preAssignedId) {
if (preAssignedId != null && !preAssignedId.isEmpty()) {
this.id = preAssignedId;
} else {
this.id = IdGenerator.generateTransactionId();
}
if (!this.id.startWith("t_")) {
this.id = "t_" + preAssignedId;
}
}
代码的输出是随机或者说不确定的，比如，跟时间、随机数有关的代码，
滥用全局变量也让编写单元测试变得困难：多个测试用例涉及到全局变量时会互相影响预期初始值
静态方法跟全局变量一样，也是一种面向过程的编程思维。在代码中调用静态方法，有时候会导致代码不易测试
Math.abs() 这样的简单静态方法，本身并不需要 mock。复杂的耗时长的静态方法需要mock
标签：prot idg string pre equals 第三方 order 也会 电商
原文地址：https://www.cnblogs.com/wod-Y/p/13045521.html
