Unit testing EF7 about entityframework.docs

[VeronicaWasson]

Two things that I didn't grok at first:

• Keep DbContext's isolated; don't re-use the same context to seed the database and then query.
• Call EnsureDeleted after each test

Another minor gotcha for me: Call EnsureDeleted before calling Assert (in xUnit), so if the assertion fails, you aren't left with stuff in the DB.

[ardalis]

If you're talking about testing that hits the database, then be sure to call it something other than unit testing. But yes, having an article on integration testing between EF and the database would be great!

[rowanmiller]

We already have #95 tracking this - EnsureDeleted is actually probably not the best as it will cause issues with multi-threaded testing. #95 has details on how to get a database scoped to each test.

[VeronicaWasson]

@ardalis: I actually meant using the InMemory provider to unit test other code that calls into EF.

@rowanmiller: Thanks!