TestDataBuilders: ValidOrder()/ValidClient() with explicit Build(); After tests migrated

Domain objects in After-side tests are constructed only through the
builders, so the upcoming OrderLines evolution changes builder internals
instead of every test. Before keeps object initializers (legacy world).

yak: testdatabuilders-validordervalidclient-after-test-migration-91vl

tests/BeforeAfter.Tests/TestData/ClientBuilder.cs

@@ -0,0 +1,40 @@
+using After;
+
+namespace BeforeAfter.Tests.TestData;
+
+/// <summary>
+/// Test data builder for a <see cref="Client"/> with its orders
+/// (TestDataBuilder pattern). <see cref="ValidClient"/> starts from a
+/// <em>fresh</em> client, exactly what <c>new Client()</c> gives.
+/// </summary>
+public sealed class ClientBuilder
+{
+    private readonly Client _client = new();
+
+    /// <summary>A valid, fresh client — the neutral starting point for tests.</summary>
+    public static ClientBuilder ValidClient() => new();
+
+    public ClientBuilder WithId(Guid id)
+    {
+        _client.Id = id;
+        return this;
+    }
+
+    public ClientBuilder WithName(string name)
+    {
+        _client.Name = name;
+        return this;
+    }
+
+    /// <summary>Adds an order to the client (navigation fix-up wires the back-reference).</summary>
+    public ClientBuilder WithOrder(Order order)
+    {
+        _client.Orders.Add(order);
+        return this;
+    }
+
+    /// <summary>Builds the given builder and adds its order — chaining sugar for <c>.WithOrder(builder.Build())</c>.</summary>
+    public ClientBuilder WithOrder(OrderBuilder order) => WithOrder(order.Build());
+
+    public Client Build() => _client;
+}

tests/BeforeAfter.Tests/TestData/OrderBuilder.cs

@@ -0,0 +1,47 @@
+using After;
+
+namespace BeforeAfter.Tests.TestData;
+
+/// <summary>
+/// Test data builder for an <see cref="Order"/> (TestDataBuilder pattern).
+/// <see cref="ValidOrder"/> starts from a <em>fresh</em> order —
+/// <see cref="Guid.Empty"/> id, empty description, zero total, exactly what
+/// <c>new Order()</c> gives — and every <c>With...</c> returns the builder for
+/// chaining; <see cref="Build"/> hands back the order.
+///
+/// This class is the only place tests touch an order's *construction*: when
+/// the domain evolves (e.g. OrderLines making the total computed), only these
+/// internals change and the tests keep reading the same.
+/// </summary>
+public sealed class OrderBuilder
+{
+    private readonly Order _order = new();
+
+    /// <summary>A valid, fresh order — the neutral starting point for tests.</summary>
+    public static OrderBuilder ValidOrder() => new();
+
+    public OrderBuilder WithId(Guid id)
+    {
+        _order.Id = id;
+        return this;
+    }
+
+    public OrderBuilder WithDescription(string description)
+    {
+        _order.Description = description;
+        return this;
+    }
+
+    /// <summary>
+    /// Sets the total in cents (<c>150_00</c> = €150.00). How the requested
+    /// total is realised inside the order is an implementation detail that may
+    /// change as the domain evolves; this API stays.
+    /// </summary>
+    public OrderBuilder WithTotal(int totalInCents)
+    {
+        _order.TotalInCents = totalInCents;
+        return this;
+    }
+
+    public Order Build() => _order;
+}