C# Unit Test NSubstitute Unable to Set Value in ObjectCache

Question

I am unable to insert a cache entry in ObjectCache with Set in my unit tests.

var objectCache = Substitute.For<ObjectCache>();
objectCache.Set("TestKey", object, Arg.Any<DateTimeOffset>());

When I step into my code

var cachedData = _objectCache.Get("TestKey");
// cachedData is null

I am using Nsubstitute for mocking libraries.

Does anyone know how to overcome this issue?

You mock the Set on a mocked object. nothing is actually being saved in the mock. You need to mock the Get for that key in order to get the desired behavior — Nkosi, Jan 24 '18 at 22:57
Not specifically related to the question, but using argument matchers as arguments to calls without `.Returns`/`.Received`/`.When`, such as `Set("TestKey", object, Arg.Any())` used in this question, can cause problems with tests. See the [docs](http://nsubstitute.github.io/help/argument-matchers/#how_not_to_use_argument_matchers) for more info. — David Tchepak, Jan 25 '18 at 02:39

score 4 · Accepted Answer · answered Jan 24 '18 at 22:59

4

You will need to configure the mock for the Get method. See the example for the return method in the NSubstitute docs.

Something like...

var objectCache = Substitute.For<ObjectCache>();
objectCache.Get("TestKey").Returns(...what you want it to return);

answered Jan 24 '18 at 22:59

Matt Stannett

1 Answers1