I just ran into the same error message.
My issue was caused by Visual Studio running the package restore via npm.
Deleting the node_modules folder and running the restore via yarn in the command line resolved the problem and allowed me to run the copy:node_modules gulp task without errors.
Thank you @ismcagdas, I will keep an eye on it.
So it seems the reason I was getting the exception is because I was running the tests with ReSharper. It was using a x64 test runner which wasn't compatible with the sqlite3.dll (x86). I was able to run the tests with VS Test explorer without a problem. Changing the build configuration to x86 for the test project allowed me to run it with ReSharper. I am now, however, getting the following three failing tests:
Should_Get_Income_Statistics_Weekly_FirstDayOfWeek() Message: Shouldly.ShouldAssertException : output.IncomeStatistics.Count should be 3 but was 4
Should_Get_Income_Statistics_Weekly_NotFirstDayOfWeek() Message: Shouldly.ShouldAssertException : output.IncomeStatistics[1].Date should be 2017-05-08T00:00:00.0000000 but was 2017-05-07T00:00:00.0000000
Create_Language() Message: Shouldly.ShouldAssertException : currentLanguages.Any(l => l.Name == newLanguageName) should be True but was False
