public void SessionStateServiceGetByIdReturnsnullWhenNotFound()
{
// arrange
SessionStateModel <TestSessionStateModel>?expectedResult = default;
var documentService = A.Fake <IDocumentService <SessionStateModel <TestSessionStateModel> > >();
A.CallTo(() => documentService.GetByIdAsync(A <Guid> .Ignored, A <string> .Ignored)).Returns(expectedResult);
var sessionStateService = new SessionStateService <TestSessionStateModel>(documentService);
// act
var result = sessionStateService.GetAsync(Guid.NewGuid()).Result;
// assert
A.CallTo(() => documentService.GetByIdAsync(A <Guid> .Ignored, A <string> .Ignored)).MustHaveHappenedOnceExactly();
A.Equals(result, expectedResult);
}