TestSupportSchema

This is a TEMPORARY project (it will move into EfCore.TestSupport when EF Core 5 is released) to contain the method EnsureClean which wipes the database schema and replaces it with a database that matches the current DbContext's configuration.

You call this via context.Database.EnsureClean().

Why is this useful?

When you are writing your unit tests you are likely to use the command context.Database.EnsureCreated() to set up the database you use for unit testing. That works for Sqlite in-memory databases, but it you are using a real database, then you need to call below to make sure that the database schema is up to date when you change the DbContext configuration or classes.

context.Database.EnsureDeleted();
context.Database.EnsureCreated();

The problem is the EnsureDeleted/EnsureCreated calls take a LONG time. This feature has the same effect (e.g. correct schema, empty of data) but is MUCH quicker e.g. for a very small database the timings are:

EF Core 5.0

What	First use	Second use	NOTES
EnsureDeleted/EnsureCreated	1.5 secs.	3 secs.	EF Core 3.1 = 10 secs.
EnsureClean	400 ms	30 ms
Respawn (see note below)	170 ms	35 ms

NOTE: Respawn is a NuGet library that removes all the rows in all the tables in a database. Useful if you have already called EnsureClean on the database and just want to remove the rows.

Where did this come from?

The idea and code came from the EF Core team. @ajcvickers described how they managed this issue and I have copied with the knowledge of the EF Core team some of EF Core's internal classes and built this feature for a Sql Server database provider.

How to use this feature

Include the EfCore.TestSupportSchema NuGet package.
Replace any EnsureDeleted/EnsureCreated calls with context.Database.EnsureClean().

Here is an example of a unit test using EfCore.TestSupport's CreateUniqueClassOptions to give you a unique database name for the test class it is in.

[Fact]
public void TestExampleOk()
{
    //SETUP
    var options = this.CreateUniqueClassOptions<YourDbContext>();
    using (var context = new YourDbContext(options))
    {
        context.Database.EnsureClean();

        //... put your unit tests here

    }
}

The EnsureClean method takes a optional boolean parameter. If set to false the method will NOT set up the tables in in the database. This is useful if you want to call context.Database.EnsureCreated() yourself.

NOTE. This only works with Sql Server databases.

What does EnsureClean remove?

It is pretty comprehensive in what it removes. i.e. indexes, foreign key constraints, tables, sequences, views, functions, aggegates, stored procedures, types.

Be warned - it DOESN'T delete the default migration table, __EFMigrationsHistory, but it does delete migration tables that don't have the normal name.