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Unit tests using Moq fail with runtime error after updating Moq to 4.20.72 (failure to load System.Threading.Tasks.Extensions) #1648
Description
Activity
@fotoware-flw Do you have a sample repo to reproduce the error ?
@fotoware-flw Our team just ran into this issue yesterday and managed to solve it, partly by coming across your post.
We ended up using binding redirects just as you posted, but the assembly version for System.Threading.Tasks.Extensions 4.6.3 is actually 4.2.1.0, not 4.2.0.1. So our redirect looks like this:
<dependentAssembly> <assemblyIdentity name="System.Threading.Tasks.Extensions" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral"/> <bindingRedirect oldVersion="0.0.0.0-4.2.1.0" newVersion="4.2.1.0"/> </dependentAssembly>
The other thing we had to do was make sure this redirect was included in every test project that used Moq. That seemed to do the trick!
Reacted by Gilles TOURREAU- added 4 commits that reference this issue
on Jun 24, 2026 - added 6 commits that reference this issue
on Jun 24, 2026 - locked and limited conversation to collaborators
on Jul 28, 2026
Describe the Bug
Unit tests using Moq fail with runtime error after updating Moq to latest version. See details below.
Steps to Reproduce
Expected Behavior
The unit tests run.
Exception with Stack Trace
Unit tests fail with error
Version Info
Additional Info
Adding binding redirects to
app.config, such asor
changes nothing.
This seems to be a recurring issue that is repeatedly being blamed on Microsoft and users of Moq, when the common denominator is always Moq. Also, in an earlier report of this issue, it was stated by the developer that Moq deliberately uses an old version of
System.Threading.Tasks.Extensionsto avoid binding redirect issues, which is clearly not the case.