Question

I am adding some test coverage to some existing code. There are about 20 classes–all derivatives of the same base class–which would result in very similar and repetitive test methods. Instead, what I’m trying to do is crate a abstract test class which exposes some abstract methods for handling the unique details of the derived class under test.

This was working well until I came to testing the ToString override. Basically, the test method (which you’ll recall lives in an abstract base class) is asserting the equality of an expected string value and the result of the ToString method executed on an instance of my generic type as provided by on the afore mentioned abstract methods. However, rather than calling the ToString override, as I was expecting, the standard object implementation is invoked instead, returning the fully-qualified name of the object.

So, the question: how can I call the ToString override of a class when dealing with a generically typed instance?

I expect this question can be answered with a better understanding of the fundamentals of generic types so, in the interest of brevity, I’m not posting any code. If I’ve underestimated the situation, please let me know and I’ll add the relevant code.

Thanks in advance!

EDIT ==> CODE 🙂

public abstract class KeyTestsBase<TKey, TKeyInterface> 
    where TKeyInterface : class
    where TKey : class, IKeyParser<TKey>
{
    protected readonly Mock<TKeyInterface> MockKey = new Mock<TKeyInterface>();

    protected abstract string ExpectedStringValue { get; }

    [Test]
    public void ToString_produces_correct_string_value()
    {
        // Arrange
        SetUpValidMock();

        // Act
        var key = BuildKey(MockKey.Object);

        var keyValue = BuildKey(MockKey.Object).ToString();

        // Assert
        Assert.AreEqual(ExpectedStringValue, keyValue);
    }

    protected abstract void SetUpValidMock();

    protected abstract TKey BuildKey(TKeyInterface keyInterface);
}

[TestFixture]
public class AdditiveProductKeyTests : KeyTestsBase<AdditiveProductKey, IAdditiveProductKey>
{
    private const int VALID_PRODUCT_KEY = 123;
    private const string VALID_PRODUCT_KEY_STRING = "123";
    private const string VALID_PARSE_INPUT = "123";

    #region Overrides of KeyTestsBase<AdditiveProductKey,IAdditiveProductKey>

    protected override string ExpectedStringValue
    {
        get { return VALID_PRODUCT_KEY_STRING; }
    }

    protected override void SetUpValidMock()
    {
        MockKey.SetupGet(m => m.AdditiveProductKey_Id).Returns(VALID_PRODUCT_KEY);
    }

    protected override AdditiveProductKey BuildKey(IAdditiveProductKey keyInterface)
    {
        return new AdditiveProductKey(keyInterface);
    }

    #endregion
}

Here’s an example of one of the many Key classes, contrary to @Marc’s suspicion, you’ll note that the ToString method is overridden.

public class AdditiveProductKey : KeyBaseClass<AdditiveProductKey>, IKey<AdditiveProduct>, IAdditiveProductKey
{
    #region constructors and fields

    private readonly int _id;

    public AdditiveProductKey() : this(0) { }

    public AdditiveProductKey(IAdditiveProductKey additiveProductKey)
        :this(additiveProductKey.AdditiveProductKey_Id) { }

    private AdditiveProductKey(int id)
    {
        _id = id;
    }

    #endregion

    public Expression<Func<AdditiveProduct, bool>> FindByPredicate
    {
        get { return (p => p.Id == _id); }
    }

    protected override AdditiveProductKey ParseImplementation(string keyValue)
    {
        var id = int.Parse(keyValue);
        return new AdditiveProductKey(id);
    }

    protected override string GetParseFailMessageImplementation()
    {
        return UserMessages.InvalidAdditiveProductKey;
    }

    public override string ToString()
    {
        return AdditiveProductKey_Id.ToString(CultureInfo.InvariantCulture);
    }

    #region Implementation of IAdditiveProductKey

    public int AdditiveProductKey_Id { get { return _id; }}

    #endregion
}

Here is the type info on the variable ‘key’ in the ToString_produces_correct_string_value test.

key.GetType()
{Name = "AdditiveProductKey" FullName = "RioValleyChili.Data.Utilities.Keys.AdditiveProductKey"}
[System.RuntimeType]: {Name = "AdditiveProductKey" FullName = "RioValleyChili.Data.Utilities.Keys.AdditiveProductKey"}
base {System.Reflection.MemberInfo}: {Name = "AdditiveProductKey" FullName = "RioValleyChili.Data.Utilities.Keys.AdditiveProductKey"}
Assembly: {RioValleyChili.Data.Utilities, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null}
AssemblyQualifiedName: "RioValleyChili.Data.Utilities.Keys.AdditiveProductKey, RioValleyChili.Data.Utilities, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"
Attributes: Public | BeforeFieldInit
BaseType: {Name = "KeyBaseClass`1" FullName = "RioValleyChili.Business.Core.Keys.KeyBaseClass`1[[RioValleyChili.Data.Utilities.Keys.AdditiveProductKey, RioValleyChili.Data.Utilities, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]"}
ContainsGenericParameters: false
DeclaringMethod: 'key.GetType().DeclaringMethod' threw an exception of type 'System.InvalidOperationException'
DeclaringType: null
FullName: "RioValleyChili.Data.Utilities.Keys.AdditiveProductKey"
GenericParameterAttributes: 'key.GetType().GenericParameterAttributes' threw an exception of type 'System.InvalidOperationException'
GenericParameterPosition: 'key.GetType().GenericParameterPosition' threw an exception of type 'System.InvalidOperationException'
GenericTypeArguments: {System.Type[0]}
GUID: {81e8adb0-f899-358b-aa20-9bec8f96666d}
HasElementType: false
IsAbstract: false
IsAnsiClass: true
IsArray: false
IsAutoClass: false
IsAutoLayout: true
IsByRef: false
IsClass: true
IsCOMObject: false
IsConstructedGenericType: false
IsContextful: false
IsEnum: false
IsExplicitLayout: false
IsGenericParameter: false
IsGenericType: false
IsGenericTypeDefinition: false
IsImport: false
IsInterface: false
IsLayoutSequential: false
IsMarshalByRef: false
IsNested: false
IsNestedAssembly: false
IsNestedFamANDAssem: false
IsNestedFamily: false
IsNestedFamORAssem: false
IsNestedPrivate: false
IsNestedPublic: false
IsNotPublic: false
IsPointer: false
IsPrimitive: false
IsPublic: true
IsSealed: false
IsSecurityCritical: true
IsSecuritySafeCritical: false
IsSecurityTransparent: false
IsSerializable: false
IsSpecialName: false
IsUnicodeClass: false
IsValueType: false
IsVisible: true
MemberType: TypeInfo
Module: {RioValleyChili.Data.Utilities.dll}
Namespace: "RioValleyChili.Data.Utilities.Keys"
ReflectedType: null
StructLayoutAttribute: {System.Runtime.InteropServices.StructLayoutAttribute}
TypeHandle: {System.RuntimeTypeHandle}
TypeInitializer: null
UnderlyingSystemType: {Name = "AdditiveProductKey" FullName = "RioValleyChili.Data.Utilities.Keys.AdditiveProductKey"}

And here are the results:

key.ToString() 
"RioValleyChili.Data.Utilities.Keys.AdditiveProductKey" //what i'm getting

((AdditiveProductKey)key).ToString()
"123" // what I'm expecting

Answer 1

ToString is a virtual/polymorphic function. As long as you have used override it should already just work. I suspect you didn’t use override.

public override string ToString() {
   // ...
}

---

Edit:

This need not be in the class you think: maybe KeyBaseClass<T> has a virtual ToString() rather than a override ToString(). This is an unrelated ToString – so your override would act on this, not object.ToString().