diff --git a/Evand-Backend/tests/DTOs/Evand.DTO.Tests.csproj b/Evand-Backend/tests/DTOs/Evand.DTO.Tests.csproj
new file mode 100644
index 00000000..8ef79469
--- /dev/null
+++ b/Evand-Backend/tests/DTOs/Evand.DTO.Tests.csproj
@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <IsPackable>false</IsPackable>
+    <Nullable>enable</Nullable>
+    <NoWarn>NU1605</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
+    <PackageReference Include="NUnit" Version="4.5.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="6.1.0" />
+    <PackageReference Include="FluentAssertions" Version="8.8.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\Evand.Application\Evand.Application.csproj" />
+    <ProjectReference Include="..\..\Evand.Domain\Evand.Domain.csproj" />
+  </ItemGroup>
+
+</Project>
\ No newline at end of file
diff --git a/Evand-Backend/tests/DTOs/UserMapperTests.cs b/Evand-Backend/tests/DTOs/UserMapperTests.cs
new file mode 100644
index 00000000..6e7dc342
--- /dev/null
+++ b/Evand-Backend/tests/DTOs/UserMapperTests.cs
@@ -0,0 +1,126 @@
+using System;
+using Evand.Application.DTOs.User;
+using FluentAssertions;
+using NUnit.Framework;
+using DomainUser = Evand.Domain.Entities.User;
+
+namespace Evand.DTO.Tests
+{
+    [TestFixture]
+    public class UserMapperTests
+    {
+        [Test]
+        public void ToDto_ShouldMapAllFields_FromDomainEntity()
+        {
+            // Arrange
+            var entity = new DomainUser
+            {
+                Guid = Guid.NewGuid(),
+                FullName = "Test User",
+                Email = "test@example.com",
+                HashPassword = "hashed-pw",
+                PhoneNumber = "09120000000",
+                City = "Tehran",
+                Province = "TehranProv",
+                Avatar = "avatar.png"
+            };
+
+            // Act
+            var dto = entity.ToDto(entity.Guid);
+
+            // Assert
+            dto.Should().NotBeNull();
+            dto.Guid.Should().Be(entity.Guid);
+            dto.FullName.Should().Be(entity.FullName);
+            dto.Email.Should().Be(entity.Email);
+            dto.HashPassword.Should().Be(entity.HashPassword);
+            dto.PhoneNumber.Should().Be(entity.PhoneNumber);
+            dto.City.Should().Be(entity.City);
+            dto.Province.Should().Be(entity.Province);
+            dto.Avatar.Should().Be(entity.Avatar);
+        }
+
+        [Test]
+        public void ToDto_ShouldPreserveNullables_FromDomainEntity()
+        {
+            // Arrange
+            var entity = new DomainUser
+            {
+                Guid = Guid.NewGuid(),
+                FullName = "Nullable User",
+                Email = "nullable@example.com",
+                HashPassword = "h",
+                PhoneNumber = null,
+                City = null,
+                Province = null,
+                Avatar = null
+            };
+
+            // Act
+            var dto = entity.ToDto(entity.Guid);
+
+            // Assert
+            dto.PhoneNumber.Should().BeNull();
+            dto.City.Should().BeNull();
+            dto.Province.Should().BeNull();
+            dto.Avatar.Should().BeNull();
+        }
+
+        [Test]
+        public void ToEntity_ShouldMapAllFields_FromAddOrUpdateDto()
+        {
+            // Arrange
+            var dto = new UserAddOrUpdateDto
+            {
+                Guid = Guid.NewGuid(),
+                FullName = "DTO User",
+                Email = "dto@example.com",
+                HashPassword = "dto-hash",
+                PhoneNumber = "09870000000",
+                City = "CityX",
+                Province = "ProvX",
+                Avatar = "dto-avatar.png"
+            };
+
+            // Act
+            var entity = dto.ToEntity();
+
+            // Assert
+            entity.Should().NotBeNull();
+            entity.Guid.Should().Be(dto.Guid);
+            entity.FullName.Should().Be(dto.FullName);
+            entity.Email.Should().Be(dto.Email);
+            entity.HashPassword.Should().Be(dto.HashPassword);
+            entity.PhoneNumber.Should().Be(dto.PhoneNumber);
+            entity.City.Should().Be(dto.City);
+            entity.Province.Should().Be(dto.Province);
+            entity.Avatar.Should().Be(dto.Avatar);
+        }
+
+        [Test]
+        public void ToEntity_ShouldPreserveNullables_FromAddOrUpdateDto()
+        {
+            // Arrange
+            var dto = new UserAddOrUpdateDto
+            {
+                Guid = Guid.NewGuid(),
+                FullName = "DTO Nulls",
+                Email = "nulls@example.com",
+                HashPassword = "h",
+                PhoneNumber = null,
+                City = null,
+                Province = null,
+                Avatar = null
+            };
+
+            // Act
+            var entity = dto.ToEntity();
+
+            // Assert
+            entity.PhoneNumber.Should().BeNull();
+            entity.City.Should().BeNull();
+            entity.Province.Should().BeNull();
+            entity.Avatar.Should().BeNull();
+        }
+    }
+}
\ No newline at end of file
diff --git a/Evand-Backend/tests/Evand.Application.Tests/EventServiceTests.cs b/Evand-Backend/tests/Evand.Application.Tests/EventServiceTests.cs
index 12abcad0..0b17725f 100644
--- a/Evand-Backend/tests/Evand.Application.Tests/EventServiceTests.cs
+++ b/Evand-Backend/tests/Evand.Application.Tests/EventServiceTests.cs
@@ -82,5 +82,25 @@ public async Task ListAsync_ShouldReturnDtos()
             result.Should().HaveCount(2);
             result.Select(r => r.Name).Should().Contain("Event1", "Event2");
         }
+
+        [Test]
+        public void AddAsync_NullDto_ShouldThrow()
+        {
+            Assert.ThrowsAsync<ArgumentNullException>(() => _service.AddAsync(null!));
+        }
+
+        [Test]
+        public void AddAsync_InvalidDates_ShouldThrow()
+        {
+            var dto = new EventAddOrUpdateDto
+            {
+                StartDate = DateTime.UtcNow.AddHours(1),
+                EndDate = DateTime.UtcNow,
+                Name = "Test",
+                Category = "Test"
+            };
+    
+        Assert.ThrowsAsync<ArgumentException>(() => _service.AddAsync(dto));
+        }   
     }
 }
\ No newline at end of file
diff --git a/Evand-Backend/tests/Evand.Application.Tests/UserServiceTests.cs b/Evand-Backend/tests/Evand.Application.Tests/UserServiceTests.cs
index 330cbaf8..0fdada2e 100644
--- a/Evand-Backend/tests/Evand.Application.Tests/UserServiceTests.cs
+++ b/Evand-Backend/tests/Evand.Application.Tests/UserServiceTests.cs
@@ -67,5 +67,27 @@ public async Task AddAsync_ValidDto_ShouldCallRepoAndSave()
             await _uow.Received(1).SaveChangesAsync(default);
         }
 
+        [Test]
+        public void AddAsync_NullDto_ShouldThrow()
+        {
+            Assert.ThrowsAsync<ArgumentNullException>(() => _service.AddAsync(null!));
+        }
+
+        [Test]
+        public async Task ListAsync_ShouldReturnUserDtos()
+        {
+            var users = new List<User>
+            {
+                new User { Guid = Guid.NewGuid(), FullName = "U1", Email = "u1@x" },
+                new User { Guid = Guid.NewGuid(), FullName = "U2", Email = "u2@x" }
+            };
+
+            _queryRepo.GetQueryable().Returns(users.AsQueryable());
+
+            var result = await _service.ListAsync();
+
+            result.Should().HaveCount(2);
+            result.Select(u => u.Email).Should().Contain("u1@x","u2@x");
+        }
     }
 }
\ No newline at end of file