How to fix bug
create new ProjectOptions with LoadTime = UtcNow for each code generation test
refactor code generation tests
Merge pull request #1 from vasily-kirichenko/fix-tests-with-same-language-service-instance

create new ProjectOptions with LoadTime = UtcNow for each code generation test
Modify protected async functions to use try/with
Merge pull request #491 from OkayX6/fix-tests-with-same-language-service-instance

What explains the tests bugs
ProjectFactory invalidates FCS before it removes ProjectProvider from its cache
remove an obsolete open declaration
remove all event listeners from VSLanguageService

ProjectFactory calls VSLanguageService.InvalidateProject only on onProjectItemChanged
Merge pull request #498 from vasily-kirichenko/fix-misbehaviour-on-added-files

ProjectFactory invalidates FCS before it removes ProjectProvider from its cache
Remove unnecessary try/with block
Merge pull request #497 from dungpa/safe-async

Modify protected async functions to use try/with
SyntaxConstructClassifier cancels running previous async computation before starting a new one

fix after rebase