Argument Display Formatters

Prova allows you to completely customize how arguments are displayed in test names using the [ArgumentDisplayFormatter] attribute. This is useful for complex types or when you want a specific representation (e.g., Hexadecimal).

Creating a Formatter

Implement the IArgumentFormatter interface.

using Prova;

public class HexFormatter : IArgumentFormatter
{
    public string Format(object? value)
    {
        if (value is int i) return $"0x{i:X}";
        return value?.ToString() ?? "null";
    }
}

Applying a Formatter

Apply the [ArgumentDisplayFormatter(typeof(YourFormatter))] attribute to test parameters.

[Fact]
[DisplayName("Checking value {0}")]
public void HexTest([Matrix(10, 255)] [ArgumentDisplayFormatter(typeof(HexFormatter))] int value)
{
    // Display name will be: Checking value 0xA
    // Display name will be: Checking value 0xFF
}

Supported Scenarios

• Combinatorial ([Matrix]): Fully supported.
• MemberData / ClassData: Supported (formatter is applied to the casted value).
• InlineData: Not yet supported (values are literals).

Best Practices

• Formatters should be lightweight and exception-safe.
• Use [DisplayName] with {0} placeholders to leverage the formatted string.