About

LightFixture is intended a faster (if less flexible) replacement for libraries like AutoFixture. While those libraries are excellent, they can become slow as the amount of anonymous data increases.

LightFixture provides source-generated factories and enables user-provided implementations to be provided for resolving anonymous data.

Installation

LightFixture is available as CNugent.LightFixture.

You can add it to your project with dotnet add {project} package CNugent.LightFixture.

Benchmark compared to AutoFixture

This is based on the LightFixture.Benchmark project within this repo.

Method	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
NarrowOfNarrow_LightFixture	759.47 ns	11.508 ns	10.764 ns	1.00	0.02	0.0353	-	592 B	1.00
NarrowOfNarrow_AutoFixture	229,561.81 ns	4,406.875 ns	4,715.307 ns	302.32	7.33	12.2070	-	205098 B	346.45
NarrowOfWide_LightFixture	17,062.51 ns	127.730 ns	113.230 ns	1.00	0.01	0.5188	-	8728 B	1.00
NarrowOfWide_AutoFixture	6,652,767.72 ns	122,484.995 ns	108,579.758 ns	389.92	6.63	320.3125	7.8125	5476059 B	627.41
NarrowStruct_LightFixture	71.82 ns	1.361 ns	1.337 ns	1.00	0.03	0.0157	-	264 B	1.00
NarrowStruct_AutoFixture	72,035.54 ns	1,405.807 ns	1,314.993 ns	1,003.34	25.17	3.7842	-	65000 B	246.21
WideOfNarrow_LightFixture	22,003.40 ns	209.782 ns	196.231 ns	1.00	0.01	0.6714	-	11456 B	1.00
WideOfNarrow_AutoFixture	7,622,914.87 ns	144,245.828 ns	148,129.846 ns	346.47	7.20	398.4375	7.8125	6682614 B	583.33
WideOfWide_LightFixture	574,385.48 ns	7,731.244 ns	7,231.810 ns	1.00	0.02	16.6016	0.9766	282656 B	1.00
WideOfWide_AutoFixture	230,612,500.53 ns	4,298,159.443 ns	4,020,501.012 ns	401.55	8.33	10000.0000	1000.0000	182904912 B	647.09

Usage

To get started with source generated providers, you can use something like the following

[DataFactory(typeof(SampleData)]
public partial class SampleDataProvider;

public sealed class SampleData
{
    public int Int { get; set; }
    
    public double? Double { get; set; }
}

Marking generates a data provider customization automatically generates all needed factories for the type trees specified. Multiple attributes can be specified together .

Data can be resolved from a DataProvider like so

var dataProvider = new DataProviderBuilder()
    .Customize(new SampleDataProvider())
    .Build();

var data = dataProvider.Resolve<SampleData>().Value;

To provide your own customizations, you can write something like

internal sealed class GuidProvider : IDataProviderCustomization
{
    public static readonly GuidProvider Instance = new();

    private GuidProvider()
    {
    }

    public void Apply(DataProviderBuilder builder)
    {
        builder.Register<Guid>(static (_, _) => Guid.NewGuid());
    }
}

or register more directly by calling either of the following on DataProviderBuilder

public DataProviderBuilder Register<T>(
    Func<DataProvider, CreationRequest?, ResolvedData<T>> factory,
    bool overrideExisting = false)
    
public DataProviderBuilder Register(
    Type type,
    Func<DataProvider, CreationRequest?, ResolvedData<object>> factory,
    bool overrideExisting = false)

Postprocessors for more granular customization can be added like so.

// specified type
builder.AddPostProcessor<BasicType>((dataProvider, bt) => bt.Value = 42);

// or less specically
buider.AddPostProcessor((dataProvider, obj) => 
{
    if(obj is BasicType bt) 
    {
        bt.Value = 42;
    }
});

Properties can be ignored during source generation like so.

[DataFactory(typeof(SampleData)]
[DataFactoryIgnoreProperty(typeof(SampleData), nameof(SampleData.Double))]
public partial class SampleDataProvider;

public sealed class SampleData
{
    public int Int { get; set; }
    
    public double? Double { get; set; }
}

LightFixture supports registration of open generics

public sealed record Wrapper<T>(T Value);

// Enables resolution of Wrapper<string>, Wrapper<int>, etc.
[DataFactory(typeof(Wrapper<>))]
public partial class SampleDataProvider;