Tutorials Entity Framework Core Tutorial
Unit Testing EF Core
Unit Testing EF Core: free step-by-step lesson with examples, common mistakes, and interview tips — part of Entity Framework Core Tutorial on Toolliyo Academy.
On this page
Entity Framework Core Tutorial · Lesson 81 of 100
Unit Testing EF Core
Beginner ✓ → Intermediate ✓ → Advanced ✓ → Professional
Professional · 4 — Real projects · ~10 min · Module 9: Testing & Debugging
What is this?
Unit tests verify application logic without real SQL — mock IProductRepository or use in-memory fakes while handlers/services run in isolation.
Why should you care?
ShopNest pricing rules should test in milliseconds without LocalDB — unit tests mock data access interfaces.
See it live — copy this example
Paste into a .NET project with EF Core packages, then run with LocalDB/SQL Server (dotnet ef / dotnet run).
[Fact]
public async Task ApplyCoupon_ReducesTotal()
{
var repo = new FakeProductRepository(new Product { Id = 1, Price = 1000 });
var svc = new PricingService(repo);
var total = await svc.ApplyCouponAsync(1, "SAVE10");
Assert.Equal(900, total);
}
class FakeProductRepository(Product p) : IProductRepository
{
public Task<Product?> GetByIdAsync(int id, CancellationToken ct) =>
Task.FromResult(id == p.Id ? p : null);
}What happened?
- FakeProductRepository returns canned Product.
- PricingService tested without DbContext.
- Fast deterministic test of business logic only.
Practice next
- Test Application services with fake repositories.
- Avoid EF InMemory in unit tests — that is integration territory.
- Use Moq or hand-written fakes per interface.
- Add test for insufficient stock using fake inventory service.
- Use Xunit theories for multiple coupon percentages.
Remember
Unit tests mock repositories not EF. Keep tests fast without database. Test business rules in Application layer.
ShopNest pricing CI
Two hundred pricing unit tests run on every PR without SQL Server service.
Outcome: Regressions caught in 10 seconds vs 10-minute integration suite.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
Sign in to ask a question or upvote helpful answers.
No questions yet — be the first to ask!
