Phase 7: Testprojekt (xUnit) + Repository-Tests

- Neues Projekt tests/PolyTrader.Tests (xUnit, EF Core InMemory-Provider),
  zur Solution hinzugefügt.
- InMemoryContextFactory<TContext>: Test-IDbContextFactory (isolierte In-Memory-DB
  je Test, geteilt über alle Kontexte einer Factory – wie im echten Betrieb).
- 18 Tests über die EF-Repos:
  - TrackedTrader: Upsert insert/update ohne Duplikat, Delete,
    AssignedAccountIds-JSON-Round-Trip (Value-Converter) + Set-Ersetzung.
  - CopyTradingAccountSettings: Upsert/Get (Dezimalwerte), Get-null, Delete.
  - CopyTradeLog: Insert/Find, Exists-Dedup (Account+Token), Predikat-Filter.
  - MasterTraderHistory: Exists-Zeitfenster, GetByTraderSince-Cutoff.
  - Core Accounts: Upsert insert/update, Delete.
- Alle 18 grün.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/PolyTrader.Tests/TrackedTraderRepositoryTests.cs

@@ -0,0 +1,74 @@
+using System.Collections.Generic;
+using System.Linq;
+using PolyTrader.Modules.CopyTrading.Persistence.Ef;
+using PolyTrader.Tests.TestSupport;
+using PolyTraderSharp.Models;
+using Xunit;
+
+namespace PolyTrader.Tests
+{
+    public class TrackedTraderRepositoryTests
+    {
+        private static EfTrackedTraderRepository NewRepo() =>
+            new(new InMemoryContextFactory<CopyTradingDbContext>(o => new CopyTradingDbContext(o)));
+
+        [Fact]
+        public void Upsert_inserts_new_trader()
+        {
+            var repo = NewRepo();
+            repo.Upsert(new TrackedTrader { Id = 1, DisplayName = "Alice" });
+
+            var all = repo.GetAll();
+            Assert.Single(all);
+            Assert.Equal("Alice", all[0].DisplayName);
+        }
+
+        [Fact]
+        public void Upsert_updates_existing_without_duplicating()
+        {
+            var repo = NewRepo();
+            repo.Upsert(new TrackedTrader { Id = 1, DisplayName = "Alice", IsActive = true });
+            repo.Upsert(new TrackedTrader { Id = 1, DisplayName = "Bob", IsActive = false });
+
+            var all = repo.GetAll();
+            Assert.Single(all);
+            Assert.Equal("Bob", all[0].DisplayName);
+            Assert.False(all[0].IsActive);
+        }
+
+        [Fact]
+        public void AssignedAccountIds_round_trips_through_json_conversion()
+        {
+            var repo = NewRepo();
+            repo.Upsert(new TrackedTrader { Id = 7, DisplayName = "X", AssignedAccountIds = new HashSet<int> { 1, 3 } });
+
+            var loaded = repo.GetAll().Single();
+            Assert.Equal(new HashSet<int> { 1, 3 }, loaded.AssignedAccountIds);
+        }
+
+        [Fact]
+        public void AssignedAccountIds_update_replaces_the_set()
+        {
+            var repo = NewRepo();
+            repo.Upsert(new TrackedTrader { Id = 7, AssignedAccountIds = new HashSet<int> { 1, 3 } });
+            repo.Upsert(new TrackedTrader { Id = 7, AssignedAccountIds = new HashSet<int> { 2 } });
+
+            var loaded = repo.GetAll().Single();
+            Assert.Equal(new HashSet<int> { 2 }, loaded.AssignedAccountIds);
+        }
+
+        [Fact]
+        public void Delete_removes_the_trader()
+        {
+            var repo = NewRepo();
+            repo.Upsert(new TrackedTrader { Id = 1 });
+            repo.Upsert(new TrackedTrader { Id = 2 });
+
+            repo.Delete(1);
+
+            var all = repo.GetAll();
+            Assert.Single(all);
+            Assert.Equal(2, all[0].Id);
+        }
+    }
+}