Add integration and unit tests for Notes API with PostgreSQL-based test hosting configuration

Freman.Sample.Web.UnitTests/Contracts/CreateNoteRequestTests.cs

@@ -0,0 +1,46 @@
+using System.ComponentModel.DataAnnotations;
+using Freman.Sample.Web.Contracts;
+using Shouldly;
+
+namespace Freman.Sample.Web.UnitTests.Contracts;
+
+public class CreateNoteRequestTests
+{
+    [Fact]
+    public void CreateNoteRequest_EmptyText_IsInvalid()
+    {
+        var model = new CreateNoteRequest { Text = "" };
+
+        var results = Validate(model);
+
+        results.Count.ShouldBeGreaterThan(0);
+    }
+
+    [Fact]
+    public void CreateNoteRequest_TooLong_IsInvalid()
+    {
+        var model = new CreateNoteRequest { Text = new string('a', 501) };
+
+        var results = Validate(model);
+
+        results.Count.ShouldBeGreaterThan(0);
+    }
+
+    [Fact]
+    public void CreateNoteRequest_NormalText_IsValid()
+    {
+        var model = new CreateNoteRequest { Text = "hello" };
+
+        var results = Validate(model);
+
+        results.Count.ShouldBe(0);
+    }
+
+    private static List<ValidationResult> Validate(object model)
+    {
+        var results = new List<ValidationResult>();
+        var ctx = new ValidationContext(model);
+        Validator.TryValidateObject(model, ctx, results, validateAllProperties: true);
+        return results;
+    }
+}