【軟體測試】Visual Studio的單元測試實作範例

【建立Bank專案】

專案範例

using System;
namespace BankAccountNS
{
    /// <summary>
    /// Bank Account demo class.
    /// </summary>
    public class BankAccount
    {
        private string m_customerName; //帳戶名稱
        private double m_balance;//帳戶餘額
        private bool m_frozen = false; //帳戶是否凍結布林變數
        private BankAccount() //建構子
        {
        }
        public BankAccount(string customerName, double balance) //建構子，傳入新增帳戶名稱和淨額/餘額(開戶金額)
        {
            m_customerName = customerName; //新增BankAccount物件中的帳戶名稱設為傳入的名稱
            m_balance = balance;//新增BankAccount物件中的淨值設為傳入的淨值
        }
        public string CustomerName //成員變數 m_customerName的存取方法
        {
            get { return m_customerName; }
        }
        public double Balance //帳戶淨值的存取方法
        {
            get { return m_balance; }
        }
        public void Debit(double amount) //從帳戶中借支，金額是由amount決定
        {
            if (m_frozen) //若帳戶凍結了
            {
                throw new Exception("Account frozen"); //程式丟出一個例外，例外字串為Account frozen，意思是帳戶凍結
            }
            if (amount > m_balance) //若要借支的金額大於帳戶的淨額
            {
                throw new ArgumentOutOfRangeException("amount"); //程式丟出一個ArgumentOutOfRangeException例外，例外字串為amount
            }
            //註：ArgumentOutOfRangeException的意思是參數超出範圍的例外
            if (amount < 0) //若要借支的金額是負值
            {
                throw new ArgumentOutOfRangeException("amount"); //程式丟出一個ArgumentOutOfRangeException例外，例外字串為amount
            }
            m_balance += amount; // intentionally incorrect code   一開始這個程式是錯誤的，借支後淨值應該是減去amount，不是加上amount，這是為了等會兒測試產生錯誤…
        }
        public void Credit(double amount) //貸款
        {
            if (m_frozen) //若帳戶凍結了
            {
                throw new Exception("Account frozen");
            }
            if (amount < 0) //若要貸款的金額是負值
            {
                throw new ArgumentOutOfRangeException("amount");
            }
            m_balance += amount; //帳戶淨額加上貸入的金額
        }
        private void FreezeAccount() //凍結帳戶方法
        {
            m_frozen = true;
        }
        private void UnfreezeAccount() //解除帳戶的凍結
        {
            m_frozen = false;
        }
        public static void Main() //主程式，程式的進入點
        {
            BankAccount ba = new BankAccount("Mr. Bryan Walton", 11.99); //新增一個BankAccount物件，帳戶名稱是Mr. Bryan Walton，開啟金額是11.99
            ba.Credit(5.77); //存款5.77
            ba.Debit(11.22); //取款11.22
            Console.WriteLine("Current balance is ${0}", ba.Balance); //印出帳戶淨額
        }
    }
}

【建立單元測試專案】

【建立測試類別】

// unit test code
using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace BankTests
{
    [TestClass]
    public class BankAccountTests
    {
        [TestMethod]
        public void TestMethod1()
        {
        }
    }
}

using BankAccountNS;

【建立第一個測試方法】

1．如果借支金額大於帳戶淨額，該方法丟出一個ArgumentOutOfRangeException例外。

2．如果借支金額小於零，該方法丟出一個ArgumentOutOfRangeException例外。

3．如果在1.) and 2.) 中的檢查通過，該方法則將帳戶淨額減去借支金額。

BankAccountTests.cs

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using BankAccountNS;
namespace BankTest
{
    [TestClass]
    public class BankAccountTests
    {
        [TestMethod]
        public void Debit_WithValidAmount_UpdatesBalance()
        {
            // arrange
            double beginningBalance = 11.99; //開戶的金額
            double debitAmount = 4.55; //借支的金額
            double expected = 7.44; //預期借支後，帳戶的預期金額
            BankAccount account = new BankAccount("Mr. Bryan Walton", beginningBalance);
            //建立BankAccount物件，名為account，上面的建構子用來指正名稱及開戶的金額
            // account物件借支debitAmount金額
            account.Debit(debitAmount);
            // assert，斷言，斷言程式不會發生指定的條件，若發生，則產生斷言例外，斷言是可以在程式正式版中關掉的。
            //斷言用來測試假設條件是否成立，當測試完都無問題後，釋出正式版本後，斷言機制就需要關閉，以提升程式的效能。
            double actual = account.Balance;
            Assert.AreEqual(expected, actual, 0.001, "Account not debited correctly");
            //斷言expected與actual兩個雙精度浮點數值相等，或在在指定精確度內(0.001)，若斷言失敗，則丟出一個AssertError。
        }
    }
}

【建置和執行測試】

1. The method throws an ArgumentOutOfRangeException if the debit amount is greater than the balance. 如果debit大於balance時，方法將會丟出ArgumentOutOfRangeException例外
2. It also throws ArgumentOutOfRangeException if the debit amount is less than zero. 如果debit小於零的話，方法也將會丟出ArgumentOutOfRangeException例外。

//unit test method
[TestMethod]
[ExpectedException(typeof(ArgumentOutOfRangeException))]
public void Debit_WhenAmountIsLessThanZero_ShouldThrowArgumentOutOfRange()
{
    // arrange
    double beginningBalance = 11.99;
    double debitAmount = -100.00;
    BankAccount account = new BankAccount("Mr. Bryan Walton", beginningBalance);
    // act
    account.Debit(debitAmount);
    // assert is handled by ExpectedException
}

1. 建立一個新的測試方法，並命名為：Debit_WhenAmountIsMoreThanBalance_ShouldThrowArgumentOutOfRange.
2. 從Debit_WhenAmountIsLessThanZero_ShouldThrowArgumentOutOfRange這個方法複製程式碼到新的方法。
3. 設定debitAmount數值大於balance餘額。

throw new ArgumentOutOfRangeException("amount");

// class under test
public const string DebitAmountExceedsBalanceMessage = "Debit amount exceeds balance";
public const string DebitAmountLessThanZeroMessage = "Debit amount less than zero";

// method under test
// ...
    if (amount > m_balance)
    {
        throw new ArgumentOutOfRangeException("amount", amount, DebitAmountExceedsBalanceMessage);
    }
    if (amount < 0)
    {
        throw new ArgumentOutOfRangeException("amount", amount, DebitAmountLessThanZeroMessage);
    }
// ...

[TestMethod]
public void Debit_WhenAmountIsMoreThanBalance_ShouldThrowArgumentOutOfRange()
{
    // arrange
    double beginningBalance = 11.99;
    double debitAmount = 20.0;
    BankAccount account = new BankAccount("Mr. Bryan Walton", beginningBalance);
    // act
    try
    {
        account.Debit(debitAmount);
    }
    catch (ArgumentOutOfRangeException e)
    {
        // assert
        StringAssert.Contains(e.Message, BankAccount. DebitAmountExceedsBalanceMessage);
    }
}

[TestMethod]
public void Debit_WhenAmountIsMoreThanBalance_ShouldThrowArgumentOutOfRange()
{
    // arrange
    double beginningBalance = 11.99;
    double debitAmount = 20.0;
    BankAccount account = new BankAccount("Mr. Bryan Walton", beginningBalance);
    // act
    try
    {
        account.Debit(debitAmount);
    }
    catch (ArgumentOutOfRangeException e)
    {
        // assert
        StringAssert.Contains(e.Message, BankAccount. DebitAmountExceedsBalanceMessage);
        return;
    }
    Assert.Fail("No exception was thrown.");
}