테스트 DB 계약과 실행 안전성 정렬

tests/KArtSell.Integration.Tests/TestDatabaseConnection.cs

@@ -0,0 +1,24 @@
+using System.Text.Json;
+
+namespace KArtSell.Integration.Tests;
+
+internal static class TestDatabaseConnection
+{
+    public static string GetConnectionString()
+    {
+        var path = Path.Combine(AppContext.BaseDirectory, "appsettings.Development.json");
+        if (!File.Exists(path))
+            throw new InvalidOperationException($"Integration test settings are required: {path}");
+
+        using var document = JsonDocument.Parse(File.ReadAllText(path));
+        if (!document.RootElement.TryGetProperty("ConnectionStrings", out var connectionStrings) ||
+            !connectionStrings.TryGetProperty("Postgres", out var postgres) ||
+            string.IsNullOrWhiteSpace(postgres.GetString()))
+        {
+            throw new InvalidOperationException(
+                "ConnectionStrings:Postgres is required in appsettings.Development.json.");
+        }
+
+        return postgres.GetString()!;
+    }
+}