Pass complex parameters to [Theory]
There are many xxxxData attributes in XUnit. Check out for example the MemberData attribute.
You can implement a property that returns IEnumerable<object[]>. Each object[] that this method generates will be then "unpacked" as a parameters for a single call to your [Theory] method.
See i.e. these examples from here
Here are some examples, just for a quick glance.
MemberData Example: just here at hand
public class StringTests2
{
[Theory, MemberData(nameof(SplitCountData))]
public void SplitCount(string input, int expectedCount)
{
var actualCount = input.Split(' ').Count();
Assert.Equal(expectedCount, actualCount);
}
public static IEnumerable<object[]> SplitCountData =>
new List<object[]>
{
new object[] { "xUnit", 1 },
new object[] { "is fun", 2 },
new object[] { "to test with", 3 }
};
}
XUnit < 2.0: Another option is ClassData, which works the same, but allows to easily share the 'generators' between tests in different classes/namespaces, and also separates the 'data generators' from the actual test methods.
ClassData Example
public class StringTests3
{
[Theory, ClassData(typeof(IndexOfData))]
public void IndexOf(string input, char letter, int expected)
{
var actual = input.IndexOf(letter);
Assert.Equal(expected, actual);
}
}
public class IndexOfData : IEnumerable<object[]>
{
private readonly List<object[]> _data = new List<object[]>
{
new object[] { "hello world", 'w', 6 },
new object[] { "goodnight moon", 'w', -1 }
};
public IEnumerator<object[]> GetEnumerator()
{ return _data.GetEnumerator(); }
IEnumerator IEnumerable.GetEnumerator()
{ return GetEnumerator(); }
}
XUnit >= 2.0: Instead of ClassData, now there's an 'overload' of [MemberData] that allows to use static members from other classes. Examples below have been updated to use it, since XUnit < 2.x is pretty ancient now.
Another option is ClassData, which works the same, but allows to easily share the 'generators' between tests in different classes/namespaces, and also separates the 'data generators' from the actual test methods.
MemberData Example: look there to another type
public class StringTests3
{
[Theory, MemberData(nameof(IndexOfData.SplitCountData), MemberType = typeof(IndexOfData))]
public void IndexOf(string input, char letter, int expected)
{
var actual = input.IndexOf(letter);
Assert.Equal(expected, actual);
}
}
public class IndexOfData : IEnumerable<object[]>
{
public static IEnumerable<object[]> SplitCountData =>
new List<object[]>
{
new object[] { "hello world", 'w', 6 },
new object[] { "goodnight moon", 'w', -1 }
};
}
Disclaimer :)
Last time checked @20210903 with dotnetfiddle.net on C# 5.0 and xunit 2.4.1 .. and failed. I couldn't mix-in a test-runner into that fiddle. But at least it compiled fine. Note that this was originally written years ago, things changed a little. I fixed them according to my hunch and comments. So.. it may contain inobvious typos, otherwise obvious bugs that would instantly pop up at runtime, and traces of milk & nuts.
To update @Quetzalcoatl's answer: The attribute [PropertyData] has been superseded by [MemberData] which takes as argument the string name of any static method, field, or property that returns an IEnumerable<object[]>. (I find it particularly nice to have an iterator method that can actually calculate test cases one at a time, yielding them up as they're computed.)
Each element in the sequence returned by the enumerator is an object[] and each array must be the same length and that length must be the number of arguments to your test case (annotated with the attribute [MemberData] and each element must have the same type as the corresponding method parameter. (Or maybe they can be convertible types, I don't know.)
(See release notes for xUnit.net March 2014 and the actual patch with example code.)
Suppose that we have a complex Car class that has a Manufacturer class:
public class Car
{
public int Id { get; set; }
public long Price { get; set; }
public Manufacturer Manufacturer { get; set; }
}
public class Manufacturer
{
public string Name { get; set; }
public string Country { get; set; }
}
We're going to fill and pass the Car class to a Theory test.
So create a 'CarClassData' class that returns an instance of the Car class like below:
public class CarClassData : IEnumerable<object[]>
{
public IEnumerator<object[]> GetEnumerator()
{
yield return new object[] {
new Car
{
Id=1,
Price=36000000,
Manufacturer = new Manufacturer
{
Country="country",
Name="name"
}
}
};
}
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}
It's time for creating a test method(CarTest) and define the car as a parameter:
[Theory]
[ClassData(typeof(CarClassData))]
public void CarTest(Car car)
{
var output = car;
var result = _myRepository.BuyCar(car);
}
**If you're going to pass a list of car objects to Theory then change the CarClassData as follow:
public class CarClassData : IEnumerable<object[]>
{
public IEnumerator<object[]> GetEnumerator()
{
yield return new object[] {
new List<Car>()
{
new Car
{
Id=1,
Price=36000000,
Manufacturer = new Manufacturer
{
Country="Iran",
Name="arya"
}
},
new Car
{
Id=2,
Price=45000,
Manufacturer = new Manufacturer
{
Country="Torbat",
Name="kurosh"
}
}
}
};
}
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}
And the theory will be:
[Theory]
[ClassData(typeof(CarClassData))]
public void CarTest(List<Car> cars)
{
var output = cars;
}
Good Luck
Creating anonymous object arrays is not the easiest way to construct the data so I used this pattern in my project.
First define some reusable, shared classes:
//http://stackoverflow.com/questions/22093843
public interface ITheoryDatum
{
object[] ToParameterArray();
}
public abstract class TheoryDatum : ITheoryDatum
{
public abstract object[] ToParameterArray();
public static ITheoryDatum Factory<TSystemUnderTest, TExpectedOutput>(TSystemUnderTest sut, TExpectedOutput expectedOutput, string description)
{
var datum= new TheoryDatum<TSystemUnderTest, TExpectedOutput>();
datum.SystemUnderTest = sut;
datum.Description = description;
datum.ExpectedOutput = expectedOutput;
return datum;
}
}
public class TheoryDatum<TSystemUnderTest, TExpectedOutput> : TheoryDatum
{
public TSystemUnderTest SystemUnderTest { get; set; }
public string Description { get; set; }
public TExpectedOutput ExpectedOutput { get; set; }
public override object[] ToParameterArray()
{
var output = new object[3];
output[0] = SystemUnderTest;
output[1] = ExpectedOutput;
output[2] = Description;
return output;
}
}
Now your individual test and member data is easier to write and cleaner...
public class IngredientTests : TestBase
{
[Theory]
[MemberData(nameof(IsValidData))]
public void IsValid(Ingredient ingredient, bool expectedResult, string testDescription)
{
Assert.True(ingredient.IsValid == expectedResult, testDescription);
}
public static IEnumerable<object[]> IsValidData
{
get
{
var food = new Food();
var quantity = new Quantity();
var data= new List<ITheoryDatum>();
data.Add(TheoryDatum.Factory(new Ingredient { Food = food } , false, "Quantity missing"));
data.Add(TheoryDatum.Factory(new Ingredient { Quantity = quantity } , false, "Food missing"));
data.Add(TheoryDatum.Factory(new Ingredient { Quantity = quantity, Food = food } , true, "Valid" ));
return data.ConvertAll(d => d.ToParameterArray());
}
}
}
The string Description property is to throw yourself a bone when one of your many test cases fail.