Viết test cho API

public class PriceCalculator
{
    public decimal Total(decimal price, int quantity)
    {
        if (quantity <= 0)
        {
            throw new ArgumentException(
                "Số lượng phải > 0");
        }

        decimal total = price * quantity;
        if (total >= 500000)
        {
            total = total * 90 / 100;
        }
        return total;
    }
}

cd ..
dotnet new xunit -o ShopApi.Tests
dotnet add ShopApi.Tests reference ShopApi
dotnet test ShopApi.Tests

using Xunit;

public class PriceCalculatorTests
{
    [Fact]
    public void Total_Under500k_NoDiscount()
    {
        var calculator = new PriceCalculator();

        decimal total = calculator.Total(100000m, 2);

        Assert.Equal(200000m, total);
    }

    [Fact]
    public void Total_ZeroQuantity_Throws()
    {
        var calculator = new PriceCalculator();

        Assert.Throws<ArgumentException>(
            () => calculator.Total(100000m, 0));
    }
}

using Xunit;

public class BoundaryTests
{
    [Fact]
    public void Total_Exactly500k()
    {
        var calculator = new PriceCalculator();

        decimal total = calculator.Total(250000m, 2);

        Assert.Equal(500000m, total);
    }
}

// SAI — test phụ thuộc file thật trên máy
using Xunit;

public class ReportTests
{
    [Fact]
    public void Read_Report()
    {
        string text =
            File.ReadAllText("C:/data/report.txt");
        Assert.NotEmpty(text);
    }
}

// ĐÚNG — bản giả trả dữ liệu định sẵn, không đọc file
public interface IReportSource
{
    string Read();
}

public class FakeReportSource : IReportSource
{
    public string Read()
    {
        return "Doanh thu: 500000";
    }
}