diff --git a/backend/src/auth-module/auth.controller.spec.ts b/backend/src/auth-module/auth.controller.spec.ts
index 517a882..bf27d7b 100644
--- a/backend/src/auth-module/auth.controller.spec.ts
+++ b/backend/src/auth-module/auth.controller.spec.ts
@@ -1,20 +1,22 @@
-import { Controller, Post, Body, HttpCode, HttpStatus } from '@nestjs/common';
+import { Test, TestingModule } from '@nestjs/testing';
+import { AuthController } from './auth.controller';
 import { AuthService } from './auth.service';
-import { RegisterDto } from './dto/register.dto';
-import { LoginDto } from './dto/login.dto';
 
-@Controller('auth')
-export class AuthController {
-  constructor(private authService: AuthService) {}
+describe('AuthController', () => {
+  let controller: AuthController;
 
-  @Post('register')
-  async register(@Body() registerDto: RegisterDto) {
-    return this.authService.register(registerDto);
-  }
+  const mockAuthService = {};
 
-  @Post('login')
-  @HttpCode(HttpStatus.OK)
-  async login(@Body() loginDto: LoginDto) {
-    return this.authService.login(loginDto);
-  }
-}
\ No newline at end of file
+  beforeEach(async () => {
+    const module: TestingModule = await Test.createTestingModule({
+      controllers: [AuthController],
+      providers: [{ provide: AuthService, useValue: mockAuthService }],
+    }).compile();
+
+    controller = module.get<AuthController>(AuthController);
+  });
+
+  it('should be defined', () => {
+    expect(controller).toBeDefined();
+  });
+});
diff --git a/backend/src/auth-module/auth.service.spec.ts b/backend/src/auth-module/auth.service.spec.ts
index 800ab66..0f00c72 100644
--- a/backend/src/auth-module/auth.service.spec.ts
+++ b/backend/src/auth-module/auth.service.spec.ts
@@ -1,15 +1,24 @@
 import { Test, TestingModule } from '@nestjs/testing';
 import { AuthService } from './auth.service';
+import { UsersService } from '../users/users.service';
 
 describe('AuthService', () => {
   let service: AuthService;
 
+  const mockUsersService = {
+    findOne: jest.fn(),
+  };
+
   beforeEach(async () => {
     const module: TestingModule = await Test.createTestingModule({
-      providers: [AuthService],
+      providers: [
+        AuthService,
+        { provide: UsersService, useValue: mockUsersService },
+      ],
     }).compile();
 
     service = module.get<AuthService>(AuthService);
+    jest.clearAllMocks();
   });
 
   it('should be defined', () => {
diff --git a/backend/src/auth-module/auth.service.ts b/backend/src/auth-module/auth.service.ts
index 05e9bf8..4eb1ecf 100644
--- a/backend/src/auth-module/auth.service.ts
+++ b/backend/src/auth-module/auth.service.ts
@@ -1,9 +1,21 @@
-import { Injectable } from '@nestjs/common';
+import { Injectable, NotFoundException } from '@nestjs/common';
 import { RegisterDto } from './dto/register.dto';
+import { UsersService } from '../users/users.service';
 
 @Injectable()
 export class AuthService {
+  constructor(private readonly usersService: UsersService) {}
+
   register(registerDto: RegisterDto) {
     throw new Error('Method not implemented.');
   }
+
+  async validateUser(userId: string) {
+    try {
+      return await this.usersService.findOne(userId);
+    } catch (e) {
+      if (e instanceof NotFoundException) return null;
+      throw e;
+    }
+  }
 }
diff --git a/backend/src/auth-module/strategies/jwt.strategy.ts b/backend/src/auth-module/strategies/jwt.strategy.ts
index 32e83c4..eabd659 100644
--- a/backend/src/auth-module/strategies/jwt.strategy.ts
+++ b/backend/src/auth-module/strategies/jwt.strategy.ts
@@ -13,7 +13,7 @@ export class JwtStrategy extends PassportStrategy(Strategy) {
     super({
       jwtFromRequest: ExtractJwt.fromAuthHeaderAsBearerToken(),
       ignoreExpiration: false,
-      secretOrKey: configService.get('JWT_SECRET'),
+      secretOrKey: configService.getOrThrow<string>('JWT_SECRET'),
     });
   }
 
diff --git a/backend/src/social-link/social-links.dto.ts b/backend/src/social-link/social-links.dto.ts
index d636c13..9bdf924 100644
--- a/backend/src/social-link/social-links.dto.ts
+++ b/backend/src/social-link/social-links.dto.ts
@@ -1,7 +1,7 @@
 import { ApiPropertyOptional } from '@nestjs/swagger';
 import { IsOptional, IsString, MaxLength } from 'class-validator';
 import { Transform } from 'class-transformer';
-import { IsSafeUrl, IsSocialHandle, sanitizeUrl, normalizeHandle } from '../common/social-links.validator';
+import { IsSafeUrl, IsSocialHandle, sanitizeUrl, normalizeHandle } from './social-links.validator';
 
 /**
  * SocialLinksDto
@@ -18,7 +18,10 @@ export class SocialLinksDto {
   @IsString()
   @MaxLength(500)
   @IsSafeUrl({ message: 'website_url must be a valid http or https URL' })
-  @Transform(({ value }) => sanitizeUrl(value))
+  @Transform(({ value }) => {
+    const sanitized = sanitizeUrl(value);
+    return sanitized !== null ? sanitized : value ?? null;
+  })
   websiteUrl?: string | null;
 
   @ApiPropertyOptional({
@@ -51,6 +54,9 @@ export class SocialLinksDto {
   @IsString()
   @MaxLength(500)
   @IsSafeUrl({ message: 'other_link must be a valid http or https URL' })
-  @Transform(({ value }) => sanitizeUrl(value))
+  @Transform(({ value }) => {
+    const sanitized = sanitizeUrl(value);
+    return sanitized !== null ? sanitized : value ?? null;
+  })
   otherLink?: string | null;
 }
diff --git a/backend/src/social-link/social-links.service.spec.ts b/backend/src/social-link/social-links.service.spec.ts
index 0a5dac1..f82c154 100644
--- a/backend/src/social-link/social-links.service.spec.ts
+++ b/backend/src/social-link/social-links.service.spec.ts
@@ -1,5 +1,5 @@
-import { SocialLinksService } from '../social-links.service';
-import { SocialLinksResponseDto } from '../dto/user-profile.dto';
+import { SocialLinksService } from './social-links.service';
+import { SocialLinksResponseDto } from './user-profile.dto';
 
 describe('SocialLinksService', () => {
   let service: SocialLinksService;
diff --git a/backend/src/social-link/social-links.service.ts b/backend/src/social-link/social-links.service.ts
index 53b76f7..8483b65 100644
--- a/backend/src/social-link/social-links.service.ts
+++ b/backend/src/social-link/social-links.service.ts
@@ -1,8 +1,8 @@
 import { Injectable } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
-import { SocialLinksDto } from '../dto/social-links.dto';
-import { SocialLinksResponseDto } from '../dto/user-profile.dto';
+import { SocialLinksDto } from './social-links.dto';
+import { SocialLinksResponseDto } from './user-profile.dto';
 
 /**
  * SocialLinksService
diff --git a/backend/src/social-link/social-links.validator.spec.ts b/backend/src/social-link/social-links.validator.spec.ts
index 79e6ede..4968518 100644
--- a/backend/src/social-link/social-links.validator.spec.ts
+++ b/backend/src/social-link/social-links.validator.spec.ts
@@ -5,8 +5,8 @@ import {
   IsSocialHandleConstraint,
   sanitizeUrl,
   normalizeHandle,
-} from '../common/social-links.validator';
-import { SocialLinksDto } from '../dto/social-links.dto';
+} from './social-links.validator';
+import { SocialLinksDto } from './social-links.dto';
 
 // ─── IsSafeUrlConstraint ─────────────────────────────────────────────────────