add unit tests

tests/Application.UnitTest/Validators/UserUpdateRequestValidatorTests.cs

@@ -0,0 +1,34 @@
+using Application.Models;
+using Application.Validators;
+
+namespace Application.UnitTest.Validators;
+
+public class UserUpdateRequestValidatorTests
+{
+    private readonly UserUpdateRequestValidator _sut = new();
+
+    [Fact]
+    public void Validate_ShouldPass_WhenAllFieldsAreValid()
+    {
+        var request = new UserUpdateRequest(1, "ValidUser", "test@example.com");
+
+        var result = _sut.Validate(request);
+
+        Assert.True(result.IsValid);
+    }
+
+    [Theory]
+    [InlineData(0, "ValidUser", "test@example.com", "Id")]
+    [InlineData(1, "", "test@example.com", "Username")]
+    [InlineData(1, "ValidUser", "", "Email")]
+    [InlineData(1, "ValidUser", "invalid-email", "Email")]
+    public void Validate_ShouldFail_WhenFieldIsInvalid(int id, string username, string email, string expectedProperty)
+    {
+        var request = new UserUpdateRequest(id, username, email);
+
+        var result = _sut.Validate(request);
+
+        Assert.False(result.IsValid);
+        Assert.Contains(result.Errors, e => e.PropertyName == expectedProperty);
+    }
+}