[Unit tests] Mocking D objects

[Simen Kjærås]

On Wednesday, 22 August 2018 at 08:33:36 UTC, Andrey wrote:
> Hello,
> I know that D has build-in unit tests. If so, what mechanism D 
> provides for mocking objects?
> For example:
>>struct WebParser
>>{
>>    // ...
>>
>>    int download(string path)
>>    {
>>        SomeHttpClient client(path);
>>        auto result = client.request(path, 10, "Qwerty");
>>
>>        // ...
>>
>>        return result.getSomething();
>>    }
>>}
>
> Here I want to replace struct/class SomeHttpClient from 
> 3d-party library with my own test implementation. Something 
> like this maybe:
> unittest
> {
>     SomeMagicMockMechanism!(SomeHttpClient, MyMockedClient);
>
>     WebParser parser;
>     auto value = parser.download("www.example.com"); // uses 
> MyMockedClient.request
>     assert(value == 10);
>
> }

The language itself does not offer mocking capabilities. However, 
there are excellent libraries in Dub:

https://code.dlang.org/packages/unit-threaded
https://code.dlang.org/packages/dmocks

--
   Simen