MaxLengthAttribute的单元测试失败

Question

我正在尝试在最大长度为25个字符的模型上测试数据注释验证。

我有这个模特：

public class ContactRequest
{
    [MaxLength(25, ErrorMessage = "String exceeds maximum length of 25")]
    public string DisplayName { get; set; }
}

但是此单元测试失败：

[Test]
public void Max25CharsTest()
{
    // Arrange
    var stringBuilder = new StringBuilder("a");

    for (var i = 0; i < 25; i++)
    {
        stringBuilder.Append("a");
    }

    var model = new ContactRequest { DisplayName = stringBuilder.ToString() };
    var context = new ValidationContext(model);

    var results = new List<ValidationResult>();

    // Act
    var actual = Validator.TryValidateObject(model, context, results);

    // Assert
    Assert.True(actual, "Expects validation to pass");

    // Append characters
    stringBuilder.Append("asdf");
    model.DisplayName = stringBuilder.ToString();
    results.Clear();
    actual = Validator.TryValidateObject(model, context, results);
    Assert.False(actual, "Expects validation to fail"); // Fails here
}

它说对象是有效的，即使不是。我在这里想念什么？

Answer 1

//...omitted for brevity

// Append characters
stringBuilder.Append("asdf");
model.DisplayName = stringBuilder.ToString() ;            
results.Clear();
actual = Validator.TryValidateObject(model, context, results, validateAllProperties: true);
Assert.IsFalse(actual, "Expects validation to fail");

注意validateAllProperties标志设置为true。这指示验证者检查所有属性，就像名称所暗示的那样

true为验证所有属性； 如果为false，则仅验证必需的属性 ..

我的重点

如果应用于测试的第一部分，由于for循环从0到25且字符串生成器已经有一个字符，它将失败。

按预期通过

public void Max25CharsTest() {
    // Arrange
    var stringBuilder = new StringBuilder("a");

    for (var i = 0; i < 24; i++) { //<-- changed this to 24
        stringBuilder.Append("a");
    }

    var model = new ContactRequest { DisplayName = stringBuilder.ToString() };
    var context = new ValidationContext(model);
    var results = new List<ValidationResult>();

    // Act
    var actual = Validator.TryValidateObject(model, context, results, validateAllProperties: true);

    // Assert
    Assert.IsTrue(actual, "Expects validation to pass");

    // Append characters
    stringBuilder.Append("asdf");
    model.DisplayName = stringBuilder.ToString();
    results.Clear();
    actual = Validator.TryValidateObject(model, context, results, validateAllProperties: true);
    Assert.IsFalse(actual, "Expects validation to fail");
}