CustomConvention.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using Fixie;
using Fixie.Conventions;

public class CustomConvention : Convention
{
    public CustomConvention()
    {
        Classes
            .NameEndsWith("Tests");

        Methods
            .Where(method => method.IsVoid());

        Parameters(method =>
        {
            //Attempt to find a perfect matching source for N calls.
            var parameters = method.GetParameters();

            if (parameters.Length == 1)
                return FindInputs(method.ReflectedType, parameters.Single().ParameterType);

            //No matching source method, so call it once with with zero parameters.
            return new[] { new object[] {} };
        });
    }

    private static IEnumerable<object[]> FindInputs(Type testClass, Type parameterType)
    {
        var enumerableOfParameterType = typeof (IEnumerable<>).MakeGenericType(parameterType);

        var sources = testClass.GetMethods(BindingFlags.Static | BindingFlags.Public)
                               .Where(m => !m.GetParameters().Any())
                               .Where(m => m.ReturnType == enumerableOfParameterType)
                               .ToArray();

        foreach (var source in sources)
            foreach (var input in (IEnumerable) source.Invoke(null, null))
                yield return new[] {input};
    }
}