Evaluation of .Net Mocking libraries

I’ve recently undertaken another round of evaluating .NET mocking (fake/substitute/dummy/stub/ or what ever you want to call them now) libraries. Interestingly the landscape has changed quite a bit since last time I went through this exercise, which was about two years ago. The outcome of the previous investigation is at the bottom of this post.

Evaluation criterion

  1. Who is the creator. I’ve favoured teams rather than individuals, as individuals move on, then where does that leave the product? RhinoMocks is a prime example of this. It’s was an excellent library. maybe a new owner, maybe not.
  2. Does it do what we need it to do?
  3. Are there any integration problems with all of our other chosen components? Works with .Net versions the development team are using. Any other complaints around integration?
  4. Cost in money. Is it free? Are there catches once you get further down the road? Usually open source projects are marketed as is. No catches
  5. Cost in time. Is the set-up painful? Customisation feedback? Upgrade feedback?
  6. How well does it appear to be supported? What do the users say?
  7. Documentation. Is there any / much? What is it’s quality?
  8. Community. Does it have an active one? Are the users getting their questions answered satisfactorily? Why are the unhappy users unhappy (do they have a valid reason).
  9. Release schedule. How often are releases being made? When was the last release?
Following is the collection of libraries I looked at. Numbering from highest scorers to lowest. All have NuGet packages:

How the Playing Field Looks Today

NSubstitute (new style)

Free and open source.
Source code: https://github.com/nsubstitute/NSubstitute/
BDFL has 534 commits. Next highest is 30.
4.5 years old. Recent activity.
Stackoverflow 69 tagged questions
Has an active Google discussion group
Regular releases
Documentation looks very good.
Very easy to read, well thought out syntax.

FakeItEasy (new style)

Free and open source.
Source code: https://github.com/FakeItEasy/FakeItEasy/
Nice spread across contributors. No single point of failure.
Almost 4 years old.
Plenty of current activity. About 30% more than NSubstitute
Stackoverflow 85 tagged questions
Regular releases
Documentation looks OK.
Syntax looks OK.


Not free and closed source.
If you happen to have a Telerik Devcraft bundle you’ll be entitled to one free JustMock license. Not much help if you want to use all the features across the team.
There is a light free version which has most/all of the features that most development teams would require.
It would have to be head and shoulders above the rest to warrant paying for it. Going on the feature set I don’t think it is, but I haven’t used it. Plus I have more confidence in the right open source offerings.
$US400 license per user.
Light edition is free, but I don’t see any reason why they couldn’t remove this offering or put a price tag on it.
NuGet package
Are we prepared to invest building code around this with the possibility of it becoming not free?
Lite vs full: http://www.telerik.com/freemocking.aspx#comparison
Doesn’t appear to be a lot of community around the free edition.


Free and open source.
Source code: https://github.com/Moq/moq4
Last release was 2013-11-18 previous to that it was 2.5 years ago.
Very small learning curve

Rhino Mocks

Free and open source.
Source code: https://github.com/hibernating-rhinos/rhino-mocks
Last activity: 3 years ago.
Has a new owner (MIke Meisinger), but I haven’t seen any new work yet.
There were also NMock and TypeMock which didn’t evaluate high enough this time or last time.
if it walks like a duck and quacks like a duck

How the Playing Field Looked Two Years Ago

Rhino Mocks

Free and open source.
Very full featured.
Easy enough to use.
logical and consistent syntax.
Most up to date documentation (best place to start)
somewhat out of date documentation, but more of it than the above link.
Community, Download, More code examples here.
Example of the old record/playback syntax as opposed to the new AAA syntax.
Keeping up to date on the progress of Rhino Mocks.
The most popular mocking framework two years ago.


Clean discoverable API design and lack of complicated record/playback model, which is nice.
Have used this, and haven’t had any issues I couldn’t get around.
Very easy to learn and use.


Commercial product (expensive, so not really viable).
Ability to mock anything including statics, privates and events on multiple languages.


Appears to be abandoned

I’ve just started using NSubstitute and have used Rhino Mocks, Moq and NMock previously.
Feel free to offer your experiences on the mocking libraries you have used and comparisons. I’d love to hear your experiences with these and other mocking libraries.

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2 Responses to “Evaluation of .Net Mocking libraries”

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