A Unit Test in Arrange-Act-Assert Style (xUnit)

using Xunit;

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

        // Act
        decimal result = calculator.ApplyDiscount(200m, 10);

        // Assert
        Assert.Equal(180m, result);
    }

    [Theory]
    [InlineData(100, 0, 100)]
    [InlineData(100, 100, 0)]
    [InlineData(50, 50, 25)]
    public void ApplyDiscount_ValidPercent_ReturnsExpected(decimal price, int percent, decimal expected)
    {
        var calculator = new PriceCalculator();

        Assert.Equal(expected, calculator.ApplyDiscount(price, percent));
    }
}

public class PriceCalculator
{
    public decimal ApplyDiscount(decimal price, int percent) => price - price * percent / 100m;
}

// Run with: dotnet test
// Test names follow Method_Scenario_ExpectedResult. Tests must be fast, isolated and deterministic.