feat(validation): add DateOfBirth rules and fix Birth null mapping

.gitignore

@@ -1,3 +1,4 @@
 logs/
 bin/
 obj/
+TestResults/

.vscode/mcp.json

@@ -0,0 +1,29 @@
+{
+  "servers": {
+    // GitHub MCP Server - Interact with GitHub APIs (issues, PRs, repos, etc.)
+    // https://github.com/github/github-mcp-server
+    "github": {
+      "type": "stdio",
+      "command": "docker",
+      "args": [
+        "run",
+        "-i",
+        "--rm",
+        "-e",
+        "GITHUB_PERSONAL_ACCESS_TOKEN",
+        "ghcr.io/github/github-mcp-server"
+      ],
+      "env": {
+        "GITHUB_PERSONAL_ACCESS_TOKEN": "${input:github_token}"
+      }
+    }
+  },
+  "inputs": [
+    {
+      "id": "github_token",
+      "type": "promptString",
+      "description": "GitHub Personal Access Token. Prefer fine-grained PATs with minimum permissions: Contents (read), Issues (read & write), Pull requests (read & write). If a classic PAT is unavoidable, minimum scope: repo.",
+      "password": true
+    }
+  ]
+}

src/Dotnet.Samples.AspNetCore.WebApi/Mappings/PlayerMappingProfile.cs

@@ -37,7 +37,12 @@ public PlayerMappingProfile()
             )
             .ForMember(
                 destination => destination.Birth,
-                options => options.MapFrom(source => $"{source.DateOfBirth:MMMM d, yyyy}")
+                options =>
+                    options.MapFrom(source =>
+                        source.DateOfBirth.HasValue
+                            ? $"{source.DateOfBirth.Value:MMMM d, yyyy}"
+                            : null
+                    )
             )
             .ForMember(
                 destination => destination.Dorsal,

src/Dotnet.Samples.AspNetCore.WebApi/Validators/PlayerRequestModelValidator.cs

@@ -39,6 +39,18 @@ public PlayerRequestModelValidator(IPlayerRepository playerRepository)
             .WithMessage("AbbrPosition is required.")
             .Must(Position.IsValidAbbr)
             .WithMessage("AbbrPosition is invalid.");
+
+        When(
+            player => player.DateOfBirth.HasValue,
+            () =>
+            {
+                RuleFor(player => player.DateOfBirth)
+                    .Must(date => date < DateTime.UtcNow)
+                    .WithMessage("DateOfBirth must be a date in the past.")
+                    .Must(date => date >= new DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc))
+                    .WithMessage("DateOfBirth must be on or after January 1, 1900.");
+            }
+        );
     }
 
     private async Task<bool> BeUniqueSquadNumber(

test/Dotnet.Samples.AspNetCore.WebApi.Tests/Unit/PlayerValidatorTests.cs

@@ -0,0 +1,225 @@
+using Dotnet.Samples.AspNetCore.WebApi.Models;
+using Dotnet.Samples.AspNetCore.WebApi.Repositories;
+using Dotnet.Samples.AspNetCore.WebApi.Tests.Utilities;
+using Dotnet.Samples.AspNetCore.WebApi.Validators;
+using FluentAssertions;
+using Moq;
+
+namespace Dotnet.Samples.AspNetCore.WebApi.Tests.Unit;
+
+public class PlayerValidatorTests
+{
+    private static PlayerRequestModelValidator CreateValidator(
+        Mock<IPlayerRepository>? repositoryMock = null
+    )
+    {
+        var mock = repositoryMock ?? new Mock<IPlayerRepository>();
+        return new PlayerRequestModelValidator(mock.Object);
+    }
+
+    /* -------------------------------------------------------------------------
+     * Valid request
+     * ---------------------------------------------------------------------- */
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenRequestModelIsValid_ThenValidationShouldPass()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        var repositoryMock = new Mock<IPlayerRepository>();
+        repositoryMock
+            .Setup(r => r.FindBySquadNumberAsync(request.SquadNumber))
+            .ReturnsAsync(null as Player);
+        var validator = CreateValidator(repositoryMock);
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeTrue();
+        result.Errors.Should().BeEmpty();
+    }
+
+    /* -------------------------------------------------------------------------
+     * FirstName
+     * ---------------------------------------------------------------------- */
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenFirstNameIsEmpty_ThenValidationShouldFail()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        request.FirstName = string.Empty;
+        var validator = CreateValidator();
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeFalse();
+        result.Errors.Should().Contain(e => e.PropertyName == "FirstName");
+    }
+
+    /* -------------------------------------------------------------------------
+     * LastName
+     * ---------------------------------------------------------------------- */
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenLastNameIsEmpty_ThenValidationShouldFail()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        request.LastName = string.Empty;
+        var validator = CreateValidator();
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeFalse();
+        result.Errors.Should().Contain(e => e.PropertyName == "LastName");
+    }
+
+    /* -------------------------------------------------------------------------
+     * SquadNumber
+     * ---------------------------------------------------------------------- */
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenSquadNumberIsNotGreaterThanZero_ThenValidationShouldFail()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        request.SquadNumber = 0;
+        var validator = CreateValidator();
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeFalse();
+        result.Errors.Should().Contain(e => e.PropertyName == "SquadNumber");
+    }
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenSquadNumberIsNotUnique_ThenValidationShouldFail()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        var existingPlayer = PlayerFakes.MakeNew();
+        var repositoryMock = new Mock<IPlayerRepository>();
+        repositoryMock
+            .Setup(r => r.FindBySquadNumberAsync(request.SquadNumber))
+            .ReturnsAsync(existingPlayer);
+        var validator = CreateValidator(repositoryMock);
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeFalse();
+        result
+            .Errors.Should()
+            .Contain(e => e.PropertyName == "SquadNumber" && e.ErrorMessage.Contains("unique"));
+    }
+
+    /* -------------------------------------------------------------------------
+     * AbbrPosition
+     * ---------------------------------------------------------------------- */
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenAbbrPositionIsEmpty_ThenValidationShouldFail()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        request.AbbrPosition = string.Empty;
+        var validator = CreateValidator();
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeFalse();
+        result.Errors.Should().Contain(e => e.PropertyName == "AbbrPosition");
+    }
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenAbbrPositionIsInvalid_ThenValidationShouldFail()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        request.AbbrPosition = "INVALID";
+        var validator = CreateValidator();
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeFalse();
+        result.Errors.Should().Contain(e => e.PropertyName == "AbbrPosition");
+    }
+
+    /* -------------------------------------------------------------------------
+     * DateOfBirth
+     * ---------------------------------------------------------------------- */
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenDateOfBirthIsNull_ThenValidationShouldPass()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        request.DateOfBirth = null;
+        var repositoryMock = new Mock<IPlayerRepository>();
+        repositoryMock
+            .Setup(r => r.FindBySquadNumberAsync(request.SquadNumber))
+            .ReturnsAsync(null as Player);
+        var validator = CreateValidator(repositoryMock);
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeTrue();
+    }
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenDateOfBirthIsInTheFuture_ThenValidationShouldFail()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        request.DateOfBirth = DateTime.UtcNow.AddYears(1);
+        var validator = CreateValidator();
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeFalse();
+        result.Errors.Should().Contain(e => e.PropertyName == "DateOfBirth");
+    }
+
+    [Fact]
+    [Trait("Category", "Unit")]
+    public async Task GivenValidateAsync_WhenDateOfBirthIsBeforeYear1900_ThenValidationShouldFail()
+    {
+        // Arrange
+        var request = PlayerFakes.MakeRequestModelForCreate();
+        request.DateOfBirth = new DateTime(1899, 12, 31, 0, 0, 0, DateTimeKind.Utc);
+        var validator = CreateValidator();
+
+        // Act
+        var result = await validator.ValidateAsync(request);
+
+        // Assert
+        result.IsValid.Should().BeFalse();
+        result.Errors.Should().Contain(e => e.PropertyName == "DateOfBirth");
+    }
+}

test/Dotnet.Samples.AspNetCore.WebApi.Tests/Utilities/PlayerFakes.cs

@@ -14,6 +14,9 @@ namespace Dotnet.Samples.AspNetCore.WebApi.Tests.Utilities;
 /// </summary>
 public static class PlayerFakes
 {
+    private static string? FormatBirth(DateTime? dateOfBirth) =>
+        dateOfBirth.HasValue ? $"{dateOfBirth.Value:MMMM d, yyyy}" : null;
+
     /// <summary>
     /// Returns the starting 11 players with generated GUIDs for in-memory testing.
     /// Reuses production player data from PlayerData.MakeStarting11().
@@ -101,7 +104,7 @@ public static PlayerResponseModel MakeResponseModelForCreate()
         {
             FullName =
                 $"{player.FirstName} {(string.IsNullOrWhiteSpace(player.MiddleName) ? "" : player.MiddleName + " ")}{player.LastName}".Trim(),
-            Birth = $"{player.DateOfBirth:MMMM d, yyyy}",
+            Birth = FormatBirth(player.DateOfBirth),
             Dorsal = player.SquadNumber,
             Position = player.Position,
             Club = player.Team,
@@ -157,7 +160,7 @@ public static PlayerResponseModel MakeResponseModelForRetrieve(int squadNumber)
         {
             FullName =
                 $"{player.FirstName} {(string.IsNullOrWhiteSpace(player.MiddleName) ? "" : player.MiddleName + " ")}{player.LastName}".Trim(),
-            Birth = $"{player.DateOfBirth:MMMM d, yyyy}",
+            Birth = FormatBirth(player.DateOfBirth),
             Dorsal = player.SquadNumber,
             Position = player.Position,
             Club = player.Team,
@@ -181,7 +184,7 @@ .. PlayerData
                     {
                         FullName =
                             $"{player.FirstName} {(string.IsNullOrWhiteSpace(player.MiddleName) ? "" : player.MiddleName + " ")}{player.LastName}".Trim(),
-                        Birth = $"{player.DateOfBirth:MMMM d, yyyy}",
+                        Birth = FormatBirth(player.DateOfBirth),
                         Dorsal = player.SquadNumber,
                         Position = player.Position,
                         Club = player.Team,