Fix ToListAsync() for mocked DbSet by using lazy-creation of AsyncEnumerator

[fischero19]

PR Details

This PR fixes ToListAsync() for mocked DbSets.

Description

In the original implementation, GetAsyncEnumerator() in BuildMockDbSet() was setup to return the current result of enumerable.GetAsyncEnumerator(). This leads to multiple issues when using ToListAsync():

• Only the initial state of the enumerable may be yielded.
• Iteration may fail with an InvalidOperationException "Collection was modified" when the collection is updated.

This fix applies only for Moq and FakeItEasy, as the NSubsitute version already used lazy returns.

Related Issue

How Has This Been Tested

• Created new test cases.
• Tested against my productive code after building the nuget package

Checklist

• [x] My code follows the code style of this project.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[romantitov]

Hi @fischero19 thanks for the PR. I will include it into the next release. As I understand the change should fix #68 and #64

[fischero19]

Hi @romantitov, thanks for maintaining this lib :). I did not explicitly test the two issues, but I also think they are fixed now.