CODEWITHSUNDEEP
c#mockingtdd
BlueTrin
BlueTrin

Reputation: 10063

How to create a mock interface for an object inheriting multiple interfaces

I am the customer of a library generating objects of class C which implements two interfaces IA and IB, which represents a permanent connection which I need to store.

I need to store the object C returned between calls.

class Example
{
    C   _obj;
}

I would like to mock the interface functions used by C for testing, but because 'C' inherits multiple interface I do not have an interface IC, so I cannot write:

class Example
{
    Example(IC cInstance) { _obj = cInstance; }
    IC  _obj;
}

therefore I cannot create easily a mock object that would implement both interfaces IA and IB which I could use for testing that my class Example works.

How do I do this without using casting or something ugly ?

Upvotes: 2

Views: 728

Answers (2)

Laurent LA RIZZA
Laurent LA RIZZA

Reputation: 2965

If the object inherits two interfaces, probably should you store two references:

class Example
{
    Example(IA aInstance, IB bInstance) { _a = aInstance; _b = bInstance; }
    IA  _a;
    IB  _b;
}

And that's not ugly. On the contrary.

Upvotes: 3

helb
helb

Reputation: 7773

You can do it using generics:

class Example<T> where T : IA, IB
{
    public Example(T instance)
    {
        this.obj = instance;
    }
    private T obj;
}

You can use C or your mockup with Example as long as that class implements both interfaces:

class CMock : IA, IB
{
    // ...
}

var myMockObj = new CMock();
var example = new Example<CMock>(myMockObj);

Upvotes: 5

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