Detect missing migrations in Entity Framework Core

Entity Framework Core allows to update the database schema using migrations. The migrations are created manually by running a CLI command. It's easy to forget to create a new migration when you change the model. To ensure the migrations are up-to-date, you can write a test that compares the current model with the snapshot model:

[Fact]
public async Task EnsureMigrationsAreUpToDate()
{
    await using var dbContext = new SampleDbContext();

    // Get required services from the dbcontext
    var migrationModelDiffer = dbContext.GetService<IMigrationsModelDiffer>();
    var migrationsAssembly = dbContext.GetService<IMigrationsAssembly>();
    var modelRuntimeInitializer = dbContext.GetService<IModelRuntimeInitializer>();
    var designTimeModel = dbContext.GetService<IDesignTimeModel>();

    // Get current model
    var model = designTimeModel.Model;

    // Get the snapshot model and finalize it
    var snapshotModel = migrationsAssembly.ModelSnapshot?.Model;
    if (snapshotModel is IMutableModel mutableModel)
    {
        // Forces post-processing on the model such that it is ready for use by the runtime
        snapshotModel = mutableModel.FinalizeModel();
    }

    if (snapshotModel is not null)
    {
        // Validates and initializes the given model with runtime dependencies
        snapshotModel = modelRuntimeInitializer.Initialize(snapshotModel);
    }

    // Compute differences
    var modelDifferences = migrationModelDiffer.GetDifferences(
            source: snapshotModel?.GetRelationalModel(),
            target: model.GetRelationalModel());

    // The differences should be empty if the migrations are up-to-date
    Assert.Empty(modelDifferences);
}

The previous code is inspired by this comment on the GitHub issue: https://github.com/dotnet/efcore/issues/26348#issuecomment-1535156915.

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