skill-ef-core-testing-expert

name	Skill: EF Core Testing Expert
description	Use when creating, reviewing, or refactoring tests for Entity Framework Core applications.

Skill: EF Core Testing Expert

Purpose

Use this skill when creating, reviewing, or refactoring tests for Entity Framework Core applications.

Primary Goals

Prioritize:

1. Correctness
2. Realistic database behavior
3. Maintainability
4. Regression protection
5. Execution speed

Tests should validate actual EF Core behavior, not assumptions.

Testing Strategy

Prefer:

• Unit tests for business logic.
• Integration tests for EF Core behavior.
• Real database providers when query translation matters.
• End-to-end tests for critical workflows.

Avoid:

• Testing EF Core internals.
• Mocking DbContext for query behavior.
• Over-reliance on the InMemory provider.

Provider Selection

Prefer:

1. Real SQL Server/PostgreSQL test database.
2. TestContainers when available.
3. SQLite in-memory when behavior is sufficiently similar.
4. EF Core InMemory only for simple non-query scenarios.

Be aware that EF Core InMemory does not behave like a relational database.

Query Testing

When testing queries:

• Verify filtering.
• Verify ordering.
• Verify paging.
• Verify projections.
• Verify includes.
• Verify generated behavior with realistic data.

Transactions

Test:

• Commit scenarios.
• Rollback scenarios.
• Nested transaction behavior.
• Savepoint behavior.
• Concurrency conflict handling.

Concurrency

Create tests for:

• Optimistic concurrency conflicts.
• Unique constraint races.
• Simultaneous updates.
• Retry logic.

Common Anti-Patterns

Avoid:

• Mocking IQueryable.
• Mocking DbSet for query validation.
• Testing EF Core framework code.
• Using InMemory provider to validate SQL behavior.
• Sharing mutable state between tests.