Added tests, need to go through them manually to check if they make sense and are correct later

Lutra/Lutra.API.IntegrationTests/Infrastructure/IntegrationTestBase.cs

@@ -0,0 +1,51 @@
+using Lutra.Application.Interfaces;
+using Lutra.Infrastructure.Sql;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Lutra.API.IntegrationTests.Infrastructure;
+
+/// <summary>
+/// Base class for integration tests. Provides a shared factory and helper methods
+/// to seed and reset the database between tests.
+/// </summary>
+public abstract class IntegrationTestBase : IClassFixture<LutraApiFactory>, IAsyncLifetime
+{
+    protected readonly LutraApiFactory Factory;
+    protected readonly HttpClient Client;
+
+    protected IntegrationTestBase(LutraApiFactory factory)
+    {
+        Factory = factory;
+        Client = factory.CreateClient();
+    }
+
+    /// <summary>Seed data or perform setup before each test.</summary>
+    public virtual Task InitializeAsync()
+    {
+        Factory.EnsureSchemaCreated();
+        return Task.CompletedTask;
+    }
+
+    /// <summary>Reset database state after each test.</summary>
+    public async Task DisposeAsync()
+    {
+        using var scope = Factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ILutraDbContext>() as LutraDbContext;
+        if (db is not null)
+        {
+            db.Beoordelingen.RemoveRange(db.Beoordelingen);
+            db.Verspaketten.RemoveRange(db.Verspaketten);
+            db.Supermarkten.RemoveRange(db.Supermarkten);
+            await db.SaveChangesAsync(CancellationToken.None);
+        }
+    }
+
+    protected async Task<T> SeedAsync<T>(T entity) where T : class
+    {
+        using var scope = Factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<ILutraDbContext>() as LutraDbContext;
+        db!.Set<T>().Add(entity);
+        await db.SaveChangesAsync(CancellationToken.None);
+        return entity;
+    }
+}