Add lightweight EF Core provider contrast sample

[balajibashyam]

Summary

Adds a minimal .NET 10 companion sample for the EF Core Testing: SQLite In-Memory vs InMemory Provider — Which One Can You Actually Trust? tutorial.

The sample is a behavioral contrast lab: one EF Core model run against both SQLite in-memory and the EF Core InMemory provider, verifying four concrete relational differences.

What's included

• New sample: ef-core/testing-sqlite-inmemory-vs-inmemory/ — 11 files

  • Shared Project + TaskItem model with unique (Name, OwnerId) index and DeleteBehavior.Cascade
  • SqliteTestDatabase helper with :memory: connection, Foreign Keys=True, explicit open lifetime
  • InMemoryTestDatabase helper with explicit InMemoryDatabaseRoot and no transaction-warning suppression
  • Four paired provider scenarios: unique constraint, foreign key, transaction rollback, database-side cascade with untracked children
  • 8 deterministic xUnit v3 tests (4 pairs showing InMemory vs SQLite contrast)
  • Deterministic six-line output (no timestamps, GUIDs, SQL, benchmark numbers)

• Root README: New sample row in the table + updated EF Core tree

• GitHub Actions: New test-ef-core-provider-contrast job (restore, build, test, package baseline, exact output, boundary checks, artifact scan)

Deliberately omitted (stays in the full tutorial)

Web API, concurrency-provider matrix, SQL Server, PostgreSQL, Testcontainers, migrations, raw SQL, JSON, temporal tables, performance benchmarking, migrations, full-text search, stored procedures.

Versions

• .NET SDK: 10.0.302
• Microsoft.EntityFrameworkCore.Sqlite: 10.0.11
• Microsoft.EntityFrameworkCore.InMemory: 10.0.11
• xunit.v3 3.2.2, xunit.runner.visualstudio 3.1.5, Microsoft.NET.Test.Sdk 18.8.1

Validation

• dotnet restore — passed
• dotnet build --configuration Release — passed (0 errors, 0 warnings)
• dotnet test --configuration Release — passed (8/8)
• App output matches the exact six-line expected block
• Security scan — clean
• No generated database artifacts