如何在 xUnit 中为 class 构造函数创建单元测试？

Question

Say I have this class:

public class BankAccount : IBankAccount
{
    public int Id { get; private set; }
    public int BankAccountNo { get; private set; }
    public decimal Balance { get; private set; }

    public BankAccount(int BankAccountNo, decimal Balance)
    {
        this.BankAccountNo = BankAccountNo;

        if(Balance <= 0)
        {
            throw new ArgumentException("Create bank account failed. Balance should be more than zero.");
        }

        this.Balance = Balance;
    }

    public void Deposit(BankTransaction bankTransaction)
    {
        if (bankTransaction.TransactionAmount <= 0)
        {
            throw new ArgumentException("Deposit failed. Transaction amount is more than account balance.");
        }

        this.Balance += bankTransaction.TransactionAmount;

        // Insert transaction record at BankTransaction Repository class
    }
}

My previous design is Deposit have BankAccount in the method parameter. With this design, I could create unit test for Deposit method as below:

    [Theory, MemberData(nameof(DepositShouldPass_Data))]
    public void DepositShouldPass(BankAccount account, BankTransaction bankTransaction, BankAccount accountExpected)
    {
        // Act
        _bankAccount.Deposit(account, bankTransaction);

        // Assert
        Assert.Equal(accountExpected.Balance, _bankAccount.Balance);
    }

    public static TheoryData<BankAccount, BankTransaction, BankAccount> DepositShouldPass_Data()
    {
        return new TheoryData<BankAccount, BankTransaction, BankAccount>
        {
            {
                new BankAccount(123, 250.00M),
                new BankTransaction(50.00M),
                new BankAccount(123, 300.00M)
            },
            {
                new BankAccount(321, 150.50M),
                new BankTransaction(10.50M),
                new BankAccount(321, 160.00M)
            }
        };
    }

But now, I want to re-design BankAccount class by removing BankAccount as method parameter in Deposit method. With this new design, how do I pass test data using xUnit? Secondly is how do I create unit test for my constructor?

Answer 1

You can try this:

var bankAccountNo = new Random().Next();
var balance = 0;
BankAccount TestCode() => new BankAccount(bankAccountNo, balance);
var exception = Assert.Throws<ArgumentException>(TestCode);
Assert.StartsWith("Create bank account failed. Balance should be more than zero.", exception.Message);

And this:

var bankAccountNo = new Random().Next();
var balance = new Random().Next();
var bankAccount = new BankAccount(bankAccountNo, balance);
Assert.Equal(bankAccountNo, bankAccount.BankAccountNo);
Assert.Equal(balance, bankAccount.Balance);