I am writing C# unit tests using NUnit and NSubstitute. I am testing a class which will attempt to retrieve objects from a config provider implementing the following interface:<
Ambiguous arguments is when NSubstitute compares the arguments to the call it is currently working with, to the stack of "argument matchers" it has (each time Arg.Blah
is called, an the argument matcher is added to that stack), and it is unable to resolve which argument goes where.
Normally this is caused by having a call like blah(null, null)
, with a single argument matcher queued up, but it can also be caused by the stack getting out-of-sync due to an arg matcher being used outside of call configuration, or as an argument to a non-virtual method.
Version 1.8.0 (released after your question) includes slightly improved detection of the latter case, so that may be worth trying.
Other than that, I've had this problem a few times and have used the following (painful) approach.
Arg.xyz
that could queue up an argument matcher in either test. Make sure it is used as part of a call configuration. Sometimes working out which call is problematic can be done by commenting out lines or replacing arg matchers with other values.Sometimes the problem may be due to a previous fixture, so you may need to workout the previous fixture and explore there as well. :(