Optimization for NUnit3

The pull request providing the ability to generate fixed name for NUnit3 has just been merged (thanks again @zvirja).

I’m working on a project containing 8,000+ tests. The discovery phase is longer than a minute. In Visual Studio there is a separate process for discovering the tests: during this phase there is no point to create the fixture nor generate the parameter values since they won’t be used (we just generate a test name TestName(auto<string>).

I successfully tested the following:

1. Have the ability to use a constructor for AutoData that takes a Func<IFixture> parameter instead of IFixture. See this line. For backward compatibility the existing constructor does still exist.
2. The IFixture factory is only invoked when argument values are required, and argument values are generated only if we are not in a discovery process. See this util type.

Please let me know if this is something that could be merged in this project, in which case I can submit a pull request. Wanted to ask you first before spending time on the pull request.

The outcome I observed is important since the discovery went from more than a minute down to a few seconds.

Let me know

[frblondin]

FYI here is my implementation - just tested succeffully 😃

    public class SkipFixtureWhenDiscoveryMethodBuilder : ITestMethodBuilder
    {
        private const string Discovery = "discovery";

        internal static bool IsDiscovery { get; private set; }

        static SkipFixtureWhenDiscoveryMethodBuilder()
        {
            try
            {
                var processName = Process.GetCurrentProcess().ProcessName;
                IsDiscovery = CultureInfo.InvariantCulture.CompareInfo.IndexOf(processName, Discovery) != -1;
            }
            catch
            {
            }
        }

        private readonly FixedNameTestMethodBuilder _fixedNameBuilder = new FixedNameTestMethodBuilder();

        public virtual TestMethod Build(IMethodInfo method, Test suite, IEnumerable<object> parameterValues, int autoDataStartIndex)
        {
            if (method == null) throw new ArgumentNullException(nameof(method));
            if (parameterValues == null) throw new ArgumentNullException(nameof(parameterValues));

            parameterValues = SkipAutoFixtureParametersIfInDiscovery(method, parameterValues, autoDataStartIndex);
            return _fixedNameBuilder.Build(method, suite, parameterValues, autoDataStartIndex);
        }

        private static IEnumerable<object> SkipAutoFixtureParametersIfInDiscovery(IMethodInfo method, IEnumerable<object> parameterValues, int autoDataStartIndex)
        {
            if (IsDiscovery)
            {
                return parameterValues.Take(autoDataStartIndex) // Only take parameter values that are not managed by AutoFixture
                   .Concat(method.GetParameters().Skip(autoDataStartIndex).Select(_ => default(object)));
            }

            return parameterValues;
        }
    }

[zvirja]

@frblondin Thanks for sharing your implementation - looks pretty clean. It’s awesome that new AutoFixture API allows you to easily perform such kind of optimizations saving the discovery time! 😃