Added tests

Tests/Musify.Application.Tests/Handlers/CreateUserCommandHandlerTests.cs

@@ -0,0 +1,44 @@
+using Ardalis.Result;
+using FluentAssertions;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using Musify.Application.Tests.Infrastructure;
+using Musify.Application.Users.Commands;
+using Musify.Application.Users.Handlers;
+using Xunit;
+
+namespace Musify.Application.Tests.Handlers;
+
+public sealed class CreateUserCommandHandlerTests
+{
+    [Fact]
+    public async Task When_user_already_exists_returns_conflict()
+    {
+        await using var ctx = new SqliteTestContext();
+        var existing = TestData.User();
+        ctx.Database.Users.Add(existing);
+        await ctx.Database.SaveChangesAsync(CancellationToken.None);
+
+        var sut = new CreateUserCommandHandler(ctx.Database, NullLogger<CreateUserCommandHandler>.Instance);
+        var result = await sut.Handle(new CreateUserCommand(existing.Id, "Bob", null, null), CancellationToken.None);
+
+        result.Status.Should().Be(ResultStatus.Conflict);
+    }
+
+    [Fact]
+    public async Task Happy_path_creates_user_and_persists()
+    {
+        await using var ctx = new SqliteTestContext();
+        var id = Guid.NewGuid();
+
+        var sut = new CreateUserCommandHandler(ctx.Database, NullLogger<CreateUserCommandHandler>.Instance);
+        var result = await sut.Handle(new CreateUserCommand(id, "Bob", "Robert", "Smith"), CancellationToken.None);
+
+        result.Status.Should().Be(ResultStatus.Created);
+        result.Value.Name.Should().Be("Bob");
+
+        var persisted = await ctx.NewContext().Users.SingleAsync(u => u.Id == id);
+        persisted.NormalizedName.Should().Be("BOB");
+        persisted.FirstName.Should().Be("Robert");
+    }
+}