feat: add dependency direction enforcement (v0.4.0)

Implement dependency direction detection to enforce Clean Architecture rules:
- Domain layer can only import from Domain and Shared
- Application layer can only import from Domain, Application, and Shared
- Infrastructure layer can import from all layers
- Shared layer can be imported by all layers

Added:
- IDependencyDirectionDetector interface in domain layer
- DependencyViolation value object with detailed suggestions and examples
- DependencyDirectionDetector implementation in infrastructure
- Integration with AnalyzeProject use case
- New DEPENDENCY_DIRECTION rule in constants
- 43 comprehensive tests covering all scenarios (100% passing)
- Good and bad examples in examples directory

Improvements:
- Optimized extractLayerFromImport method to reduce complexity
- Fixed indentation in DependencyGraph.ts
- Updated getExampleFix to avoid false positives in old detector

Test Results:
- All 261 tests passing
- Build successful
- Self-check: 0 architecture violations in src code

packages/guardian/ROADMAP.md

@@ -2,7 +2,7 @@
 
 This document outlines the current features and future plans for @puaros/guardian.
 
-## Current Version: 0.3.0 ✅ RELEASED
+## Current Version: 0.4.0 ✅ RELEASED
 
 **Released:** 2025-11-24
 
@@ -71,10 +71,9 @@ async getUser(id: string): Promise<UserResponseDto> {
 
 ---
 
-## Future Roadmap
+## Version 0.4.0 - Dependency Direction Enforcement 🎯 ✅ RELEASED
 
-### Version 0.4.0 - Dependency Direction Enforcement 🎯
-**Target:** Q1 2026
+**Released:** 2025-11-24
 **Priority:** HIGH
 
 Enforce correct dependency direction between architectural layers:
@@ -103,16 +102,20 @@ import { User } from '../../domain/entities/User'  // OK
 - ✅ Infrastructure → Application, Domain (разрешено)
 - ✅ Shared → используется везде
 
-**Planned Features:**
-- Detect domain importing from application
-- Detect domain importing from infrastructure
-- Detect application importing from infrastructure
-- Visualize dependency graph
-- Suggest refactoring to fix violations
-- Support for custom layer definitions
+**Implemented Features:**
+- ✅ Detect domain importing from application
+- ✅ Detect domain importing from infrastructure
+- ✅ Detect application importing from infrastructure
+- ✅ Detect violations in all import formats (ES6, require)
+- ✅ Provide detailed error messages with suggestions
+- ✅ Show example fixes for each violation type
+- ✅ 43 tests covering all dependency scenarios
+- ✅ Good and bad examples in examples directory
 
 ---
 
+## Future Roadmap
+
 ### Version 0.5.0 - Repository Pattern Validation 📚
 **Target:** Q1 2026
 **Priority:** HIGH
@@ -1748,4 +1751,4 @@ Until we reach 1.0.0, minor version bumps (0.x.0) may include breaking changes a
 ---
 
 **Last Updated:** 2025-11-24
-**Current Version:** 0.3.0
+**Current Version:** 0.4.0

packages/guardian/examples/bad-architecture/dependency-direction/BadApplicationLayer.ts

@@ -0,0 +1,117 @@
+/**
+ * ❌ BAD: Application layer with incorrect dependencies
+ *
+ * Application importing from Infrastructure layer
+ * This violates Clean Architecture dependency rules!
+ */
+
+import { User } from "../../good-architecture/domain/entities/User"
+import { Email } from "../../good-architecture/domain/value-objects/Email"
+import { UserId } from "../../good-architecture/domain/value-objects/UserId"
+
+/**
+ * ❌ VIOLATION: Application importing from Infrastructure layer
+ */
+import { PrismaClient } from "@prisma/client"
+
+export class CreateUser {
+    /**
+     * ❌ VIOLATION: Application use case depending on concrete infrastructure (Prisma)
+     */
+    constructor(private prisma: PrismaClient) {}
+
+    async execute(email: string): Promise<User> {
+        const userId = UserId.generate()
+        const emailVO = Email.create(email).value
+
+        /**
+         * ❌ VIOLATION: Application logic directly accessing database
+         */
+        await this.prisma.user.create({
+            data: {
+                id: userId.getValue(),
+                email: emailVO.getValue(),
+            },
+        })
+
+        return new User(userId, emailVO)
+    }
+}
+
+/**
+ * ❌ VIOLATION: Application importing concrete email service from infrastructure
+ */
+import { SmtpEmailService } from "../../good-architecture/infrastructure/adapters/SmtpEmailService"
+
+export class SendWelcomeEmail {
+    /**
+     * ❌ VIOLATION: Application depending on concrete infrastructure implementation
+     * Should depend on IEmailService interface instead
+     */
+    constructor(
+        private prisma: PrismaClient,
+        private emailService: SmtpEmailService,
+    ) {}
+
+    async execute(userId: string): Promise<void> {
+        const user = await this.prisma.user.findUnique({
+            where: { id: userId },
+        })
+
+        if (!user) {
+            throw new Error("User not found")
+        }
+
+        await this.emailService.sendWelcomeEmail(user.email)
+    }
+}
+
+/**
+ * ❌ VIOLATION: Application importing from infrastructure controller
+ */
+import { UserController } from "../../good-architecture/infrastructure/controllers/UserController"
+
+export class ValidateUser {
+    /**
+     * ❌ VIOLATION: Application use case depending on infrastructure controller
+     * The dependency direction is completely wrong!
+     */
+    constructor(private userController: UserController) {}
+
+    async execute(userId: string): Promise<boolean> {
+        return true
+    }
+}
+
+/**
+ * ❌ VIOLATION: Application importing HTTP framework
+ */
+import express from "express"
+
+export class ProcessUserRequest {
+    /**
+     * ❌ VIOLATION: Application layer knows about HTTP/Express
+     * HTTP concerns should be in infrastructure layer
+     */
+    async execute(req: express.Request): Promise<void> {
+        const email = req.body.email
+        console.log(`Processing user: ${email}`)
+    }
+}
+
+/**
+ * ❌ VIOLATION: Application importing infrastructure repository implementation
+ */
+import { InMemoryUserRepository } from "../../good-architecture/infrastructure/repositories/InMemoryUserRepository"
+
+export class GetUser {
+    /**
+     * ❌ VIOLATION: Application depending on concrete repository implementation
+     * Should depend on IUserRepository interface from domain
+     */
+    constructor(private userRepo: InMemoryUserRepository) {}
+
+    async execute(userId: string): Promise<User | null> {
+        return await this.userRepo.findById(UserId.from(userId))
+    }
+}

packages/guardian/examples/bad-architecture/dependency-direction/BadDomainLayer.ts

@@ -0,0 +1,90 @@
+/**
+ * ❌ BAD: Domain layer with incorrect dependencies
+ *
+ * Domain importing from Application and Infrastructure layers
+ * This violates Clean Architecture dependency rules!
+ */
+
+import { Email } from "../../good-architecture/domain/value-objects/Email"
+import { UserId } from "../../good-architecture/domain/value-objects/UserId"
+
+/**
+ * ❌ VIOLATION: Domain importing from Application layer
+ */
+import { UserResponseDto } from "../../good-architecture/application/dtos/UserResponseDto"
+
+export class User {
+    private readonly id: UserId
+    private email: Email
+
+    constructor(id: UserId, email: Email) {
+        this.id = id
+        this.email = email
+    }
+
+    /**
+     * ❌ VIOLATION: Domain entity returning DTO from application layer
+     */
+    toDto(): UserResponseDto {
+        return {
+            id: this.id.getValue(),
+            email: this.email.getValue(),
+            createdAt: new Date().toISOString(),
+        }
+    }
+}
+
+/**
+ * ❌ VIOLATION: Domain importing from Infrastructure layer
+ */
+import { PrismaClient } from "@prisma/client"
+
+export class UserService {
+    /**
+     * ❌ VIOLATION: Domain service depending on concrete infrastructure implementation
+     */
+    constructor(private prisma: PrismaClient) {}
+
+    async createUser(email: string): Promise<User> {
+        const userId = UserId.generate()
+        const emailVO = Email.create(email).value
+
+        /**
+         * ❌ VIOLATION: Domain logic directly accessing database
+         */
+        await this.prisma.user.create({
+            data: {
+                id: userId.getValue(),
+                email: emailVO.getValue(),
+            },
+        })
+
+        return new User(userId, emailVO)
+    }
+}
+
+/**
+ * ❌ VIOLATION: Domain importing email service from infrastructure
+ */
+import { SmtpEmailService } from "../../good-architecture/infrastructure/adapters/SmtpEmailService"
+
+export class UserRegistration {
+    /**
+     * ❌ VIOLATION: Domain depending on infrastructure email service
+     */
+    constructor(
+        private userService: UserService,
+        private emailService: SmtpEmailService,
+    ) {}
+
+    async register(email: string): Promise<User> {
+        const user = await this.userService.createUser(email)
+
+        /**
+         * ❌ VIOLATION: Domain calling infrastructure service directly
+         */
+        await this.emailService.sendWelcomeEmail(email)
+
+        return user
+    }
+}

packages/guardian/examples/good-architecture/dependency-direction/GoodApplicationLayer.ts

@@ -0,0 +1,91 @@
+/**
+ * ✅ GOOD: Application layer with correct dependencies
+ *
+ * Application should only import from:
+ * - Domain layer
+ * - Other application files
+ * - Shared utilities
+ *
+ * Application should NOT import from:
+ * - Infrastructure layer
+ */
+
+import { User } from "../domain/entities/User"
+import { Email } from "../domain/value-objects/Email"
+import { UserId } from "../domain/value-objects/UserId"
+import { IUserRepository } from "../domain/repositories/IUserRepository"
+import { Result } from "../../../src/shared/types/Result"
+
+/**
+ * ✅ Use case depends on domain interfaces (IUserRepository)
+ * NOT on infrastructure implementations
+ */
+export class CreateUser {
+    constructor(private readonly userRepo: IUserRepository) {}
+
+    async execute(request: CreateUserRequest): Promise<Result<UserResponseDto>> {
+        const emailResult = Email.create(request.email)
+        if (emailResult.isFailure) {
+            return Result.fail(emailResult.error)
+        }
+
+        const userId = UserId.generate()
+        const user = new User(userId, emailResult.value)
+
+        await this.userRepo.save(user)
+
+        return Result.ok(UserMapper.toDto(user))
+    }
+}
+
+/**
+ * ✅ DTO in application layer
+ */
+export interface CreateUserRequest {
+    email: string
+    name: string
+}
+
+export interface UserResponseDto {
+    id: string
+    email: string
+    createdAt: string
+}
+
+/**
+ * ✅ Mapper in application layer converting domain to DTO
+ */
+export class UserMapper {
+    static toDto(user: User): UserResponseDto {
+        return {
+            id: user.getId().getValue(),
+            email: user.getEmail().getValue(),
+            createdAt: user.getCreatedAt().toISOString(),
+        }
+    }
+}
+
+/**
+ * ✅ Application defines Port (interface) for email service
+ * Infrastructure will provide the Adapter (implementation)
+ */
+export interface IEmailService {
+    sendWelcomeEmail(email: string): Promise<void>
+}
+
+export class SendWelcomeEmail {
+    constructor(
+        private readonly userRepo: IUserRepository,
+        private readonly emailService: IEmailService,
+    ) {}
+
+    async execute(userId: string): Promise<Result<void>> {
+        const user = await this.userRepo.findById(UserId.from(userId))
+        if (!user) {
+            return Result.fail("User not found")
+        }
+
+        await this.emailService.sendWelcomeEmail(user.getEmail().getValue())
+        return Result.ok()
+    }
+}

packages/guardian/examples/good-architecture/dependency-direction/GoodDomainLayer.ts

@@ -0,0 +1,56 @@
+/**
+ * ✅ GOOD: Domain layer with correct dependencies
+ *
+ * Domain should only import from:
+ * - Other domain files
+ * - Shared utilities
+ *
+ * Domain should NOT import from:
+ * - Application layer
+ * - Infrastructure layer
+ */
+
+import { Email } from "../domain/value-objects/Email"
+import { UserId } from "../domain/value-objects/UserId"
+import { Result } from "../../../src/shared/types/Result"
+
+/**
+ * ✅ Domain entity using only domain value objects and shared types
+ */
+export class User {
+    private readonly id: UserId
+    private email: Email
+    private readonly createdAt: Date
+
+    constructor(id: UserId, email: Email, createdAt: Date = new Date()) {
+        this.id = id
+        this.email = email
+        this.createdAt = createdAt
+    }
+
+    public getId(): UserId {
+        return this.id
+    }
+
+    public getEmail(): Email {
+        return this.email
+    }
+
+    public changeEmail(newEmail: Email): Result<void> {
+        if (this.email.equals(newEmail)) {
+            return Result.fail("Email is the same")
+        }
+
+        this.email = newEmail
+        return Result.ok()
+    }
+}
+
+/**
+ * ✅ Domain repository interface (not importing from infrastructure)
+ */
+export interface IUserRepository {
+    findById(id: UserId): Promise<User | null>
+    save(user: User): Promise<void>
+    delete(id: UserId): Promise<void>
+}

packages/guardian/examples/good-architecture/dependency-direction/GoodInfrastructureLayer.ts

@@ -0,0 +1,128 @@
+/**
+ * ✅ GOOD: Infrastructure layer with correct dependencies
+ *
+ * Infrastructure CAN import from:
+ * - Domain layer
+ * - Application layer
+ * - Other infrastructure files
+ * - Shared utilities
+ * - External libraries (ORM, frameworks, etc.)
+ */
+
+import { User } from "../domain/entities/User"
+import { UserId } from "../domain/value-objects/UserId"
+import { Email } from "../domain/value-objects/Email"
+import { IUserRepository } from "../domain/repositories/IUserRepository"
+import { CreateUser } from "../application/use-cases/CreateUser"
+import { UserResponseDto } from "../application/dtos/UserResponseDto"
+import { IEmailService } from "../application/ports/IEmailService"
+
+/**
+ * ✅ Infrastructure implements domain interface
+ */
+export class InMemoryUserRepository implements IUserRepository {
+    private users: Map<string, User> = new Map()
+
+    async findById(id: UserId): Promise<User | null> {
+        return this.users.get(id.getValue()) ?? null
+    }
+
+    async save(user: User): Promise<void> {
+        this.users.set(user.getId().getValue(), user)
+    }
+
+    async delete(id: UserId): Promise<void> {
+        this.users.delete(id.getValue())
+    }
+}
+
+/**
+ * ✅ Infrastructure provides Adapter implementing application Port
+ */
+export class SmtpEmailService implements IEmailService {
+    constructor(
+        private readonly host: string,
+        private readonly port: number,
+    ) {}
+
+    async sendWelcomeEmail(email: string): Promise<void> {
+        console.log(`Sending welcome email to ${email} via SMTP`)
+    }
+}
+
+/**
+ * ✅ Controller uses application use cases and DTOs
+ */
+export class UserController {
+    constructor(private readonly createUser: CreateUser) {}
+
+    async create(request: { email: string; name: string }): Promise<UserResponseDto> {
+        const result = await this.createUser.execute(request)
+
+        if (result.isFailure) {
+            throw new Error(result.error)
+        }
+
+        return result.value
+    }
+}
+
+/**
+ * ✅ Infrastructure can use external frameworks
+ */
+import express from "express"
+
+export class ExpressServer {
+    private app = express()
+
+    constructor(private readonly userController: UserController) {
+        this.setupRoutes()
+    }
+
+    private setupRoutes(): void {
+        this.app.post("/users", async (req, res) => {
+            const user = await this.userController.create(req.body)
+            res.json(user)
+        })
+    }
+}
+
+/**
+ * ✅ Infrastructure can use ORM
+ */
+import { PrismaClient } from "@prisma/client"
+
+export class PrismaUserRepository implements IUserRepository {
+    constructor(private readonly prisma: PrismaClient) {}
+
+    async findById(id: UserId): Promise<User | null> {
+        const userData = await this.prisma.user.findUnique({
+            where: { id: id.getValue() },
+        })
+
+        if (!userData) {
+            return null
+        }
+
+        return new User(UserId.from(userData.id), Email.create(userData.email).value)
+    }
+
+    async save(user: User): Promise<void> {
+        await this.prisma.user.upsert({
+            where: { id: user.getId().getValue() },
+            create: {
+                id: user.getId().getValue(),
+                email: user.getEmail().getValue(),
+            },
+            update: {
+                email: user.getEmail().getValue(),
+            },
+        })
+    }
+
+    async delete(id: UserId): Promise<void> {
+        await this.prisma.user.delete({
+            where: { id: id.getValue() },
+        })
+    }
+}

packages/guardian/package.json

@@ -1,6 +1,6 @@
 {
     "name": "@samiyev/guardian",
-    "version": "0.3.0",
+    "version": "0.4.0",
     "description": "Code quality guardian for vibe coders and enterprise teams - catch hardcodes, architecture violations, and circular deps. Enforce Clean Architecture at scale. Works with Claude, GPT, Copilot.",
     "keywords": [
         "puaros",

packages/guardian/src/api.ts

@@ -9,12 +9,14 @@ import { IHardcodeDetector } from "./domain/services/IHardcodeDetector"
 import { INamingConventionDetector } from "./domain/services/INamingConventionDetector"
 import { IFrameworkLeakDetector } from "./domain/services/IFrameworkLeakDetector"
 import { IEntityExposureDetector } from "./domain/services/IEntityExposureDetector"
+import { IDependencyDirectionDetector } from "./domain/services/IDependencyDirectionDetector"
 import { FileScanner } from "./infrastructure/scanners/FileScanner"
 import { CodeParser } from "./infrastructure/parsers/CodeParser"
 import { HardcodeDetector } from "./infrastructure/analyzers/HardcodeDetector"
 import { NamingConventionDetector } from "./infrastructure/analyzers/NamingConventionDetector"
 import { FrameworkLeakDetector } from "./infrastructure/analyzers/FrameworkLeakDetector"
 import { EntityExposureDetector } from "./infrastructure/analyzers/EntityExposureDetector"
+import { DependencyDirectionDetector } from "./infrastructure/analyzers/DependencyDirectionDetector"
 import { ERROR_MESSAGES } from "./shared/constants"
 
 /**
@@ -69,6 +71,8 @@ export async function analyzeProject(
     const namingConventionDetector: INamingConventionDetector = new NamingConventionDetector()
     const frameworkLeakDetector: IFrameworkLeakDetector = new FrameworkLeakDetector()
     const entityExposureDetector: IEntityExposureDetector = new EntityExposureDetector()
+    const dependencyDirectionDetector: IDependencyDirectionDetector =
+        new DependencyDirectionDetector()
     const useCase = new AnalyzeProject(
         fileScanner,
         codeParser,
@@ -76,6 +80,7 @@ export async function analyzeProject(
         namingConventionDetector,
         frameworkLeakDetector,
         entityExposureDetector,
+        dependencyDirectionDetector,
     )
 
     const result = await useCase.execute(options)
@@ -96,5 +101,6 @@ export type {
     NamingConventionViolation,
     FrameworkLeakViolation,
     EntityExposureViolation,
+    DependencyDirectionViolation,
     ProjectMetrics,
 } from "./application/use-cases/AnalyzeProject"

packages/guardian/src/application/use-cases/AnalyzeProject.ts

@@ -6,6 +6,7 @@ import { IHardcodeDetector } from "../../domain/services/IHardcodeDetector"
 import { INamingConventionDetector } from "../../domain/services/INamingConventionDetector"
 import { IFrameworkLeakDetector } from "../../domain/services/IFrameworkLeakDetector"
 import { IEntityExposureDetector } from "../../domain/services/IEntityExposureDetector"
+import { IDependencyDirectionDetector } from "../../domain/services/IDependencyDirectionDetector"
 import { SourceFile } from "../../domain/entities/SourceFile"
 import { DependencyGraph } from "../../domain/entities/DependencyGraph"
 import { ProjectPath } from "../../domain/value-objects/ProjectPath"
@@ -34,6 +35,7 @@ export interface AnalyzeProjectResponse {
     namingViolations: NamingConventionViolation[]
     frameworkLeakViolations: FrameworkLeakViolation[]
     entityExposureViolations: EntityExposureViolation[]
+    dependencyDirectionViolations: DependencyDirectionViolation[]
     metrics: ProjectMetrics
 }
 
@@ -109,6 +111,17 @@ export interface EntityExposureViolation {
     suggestion: string
 }
 
+export interface DependencyDirectionViolation {
+    rule: typeof RULES.DEPENDENCY_DIRECTION
+    fromLayer: string
+    toLayer: string
+    importPath: string
+    file: string
+    line?: number
+    message: string
+    suggestion: string
+}
+
 export interface ProjectMetrics {
     totalFiles: number
     totalFunctions: number
@@ -130,6 +143,7 @@ export class AnalyzeProject extends UseCase<
         private readonly namingConventionDetector: INamingConventionDetector,
         private readonly frameworkLeakDetector: IFrameworkLeakDetector,
         private readonly entityExposureDetector: IEntityExposureDetector,
+        private readonly dependencyDirectionDetector: IDependencyDirectionDetector,
     ) {
         super()
     }
@@ -180,6 +194,7 @@ export class AnalyzeProject extends UseCase<
             const namingViolations = this.detectNamingConventions(sourceFiles)
             const frameworkLeakViolations = this.detectFrameworkLeaks(sourceFiles)
             const entityExposureViolations = this.detectEntityExposures(sourceFiles)
+            const dependencyDirectionViolations = this.detectDependencyDirections(sourceFiles)
             const metrics = this.calculateMetrics(sourceFiles, totalFunctions, dependencyGraph)
 
             return ResponseDto.ok({
@@ -191,6 +206,7 @@ export class AnalyzeProject extends UseCase<
                 namingViolations,
                 frameworkLeakViolations,
                 entityExposureViolations,
+                dependencyDirectionViolations,
                 metrics,
             })
         } catch (error) {
@@ -409,6 +425,33 @@ export class AnalyzeProject extends UseCase<
         return violations
     }
 
+    private detectDependencyDirections(sourceFiles: SourceFile[]): DependencyDirectionViolation[] {
+        const violations: DependencyDirectionViolation[] = []
+
+        for (const file of sourceFiles) {
+            const directionViolations = this.dependencyDirectionDetector.detectViolations(
+                file.content,
+                file.path.relative,
+                file.layer,
+            )
+
+            for (const violation of directionViolations) {
+                violations.push({
+                    rule: RULES.DEPENDENCY_DIRECTION,
+                    fromLayer: violation.fromLayer,
+                    toLayer: violation.toLayer,
+                    importPath: violation.importPath,
+                    file: file.path.relative,
+                    line: violation.line,
+                    message: violation.getMessage(),
+                    suggestion: violation.getSuggestion(),
+                })
+            }
+        }
+
+        return violations
+    }
+
     private calculateMetrics(
         sourceFiles: SourceFile[],
         totalFunctions: number,

packages/guardian/src/domain/services/IDependencyDirectionDetector.ts

@@ -0,0 +1,47 @@
+import { DependencyViolation } from "../value-objects/DependencyViolation"
+
+/**
+ * Interface for detecting dependency direction violations in the codebase
+ *
+ * Dependency direction violations occur when a layer imports from a layer
+ * that it should not depend on according to Clean Architecture principles:
+ * - Domain should not import from Application or Infrastructure
+ * - Application should not import from Infrastructure
+ * - Infrastructure can import from Application and Domain
+ * - Shared can be imported by all layers
+ */
+export interface IDependencyDirectionDetector {
+    /**
+     * Detects dependency direction violations in the given code
+     *
+     * Analyzes import statements to identify violations of dependency rules
+     * between architectural layers.
+     *
+     * @param code - Source code to analyze
+     * @param filePath - Path to the file being analyzed
+     * @param layer - The architectural layer of the file (domain, application, infrastructure, shared)
+     * @returns Array of detected dependency direction violations
+     */
+    detectViolations(
+        code: string,
+        filePath: string,
+        layer: string | undefined,
+    ): DependencyViolation[]
+
+    /**
+     * Checks if an import violates dependency direction rules
+     *
+     * @param fromLayer - The layer that is importing
+     * @param toLayer - The layer being imported
+     * @returns True if the import violates dependency rules
+     */
+    isViolation(fromLayer: string, toLayer: string): boolean
+
+    /**
+     * Extracts the layer from an import path
+     *
+     * @param importPath - The import path to analyze
+     * @returns The layer name if detected, undefined otherwise
+     */
+    extractLayerFromImport(importPath: string): string | undefined
+}

packages/guardian/src/domain/value-objects/DependencyViolation.ts

@@ -0,0 +1,162 @@
+import { ValueObject } from "./ValueObject"
+
+interface DependencyViolationProps {
+    readonly fromLayer: string
+    readonly toLayer: string
+    readonly importPath: string
+    readonly filePath: string
+    readonly line?: number
+}
+
+/**
+ * Represents a dependency direction violation in the codebase
+ *
+ * Dependency direction violations occur when a layer imports from a layer
+ * that it should not depend on according to Clean Architecture principles:
+ * - Domain → should not import from Application or Infrastructure
+ * - Application → should not import from Infrastructure
+ * - Infrastructure → can import from Application and Domain (allowed)
+ * - Shared → can be imported by all layers (allowed)
+ *
+ * @example
+ * ```typescript
+ * // Bad: Domain importing from Application
+ * const violation = DependencyViolation.create(
+ *     'domain',
+ *     'application',
+ *     '../../application/dtos/UserDto',
+ *     'src/domain/entities/User.ts',
+ *     5
+ * )
+ *
+ * console.log(violation.getMessage())
+ * // "Domain layer should not import from Application layer"
+ * ```
+ */
+export class DependencyViolation extends ValueObject<DependencyViolationProps> {
+    private constructor(props: DependencyViolationProps) {
+        super(props)
+    }
+
+    public static create(
+        fromLayer: string,
+        toLayer: string,
+        importPath: string,
+        filePath: string,
+        line?: number,
+    ): DependencyViolation {
+        return new DependencyViolation({
+            fromLayer,
+            toLayer,
+            importPath,
+            filePath,
+            line,
+        })
+    }
+
+    public get fromLayer(): string {
+        return this.props.fromLayer
+    }
+
+    public get toLayer(): string {
+        return this.props.toLayer
+    }
+
+    public get importPath(): string {
+        return this.props.importPath
+    }
+
+    public get filePath(): string {
+        return this.props.filePath
+    }
+
+    public get line(): number | undefined {
+        return this.props.line
+    }
+
+    public getMessage(): string {
+        return `${this.capitalizeFirst(this.props.fromLayer)} layer should not import from ${this.capitalizeFirst(this.props.toLayer)} layer`
+    }
+
+    public getSuggestion(): string {
+        const suggestions: string[] = []
+
+        if (this.props.fromLayer === "domain") {
+            suggestions.push(
+                "Domain layer should be independent and not depend on other layers",
+                "Move the imported code to the domain layer if it contains business logic",
+                "Use dependency inversion: define an interface in domain and implement it in infrastructure",
+            )
+        } else if (this.props.fromLayer === "application") {
+            suggestions.push(
+                "Application layer should not depend on infrastructure",
+                "Define an interface (Port) in application layer",
+                "Implement the interface (Adapter) in infrastructure layer",
+                "Use dependency injection to provide the implementation",
+            )
+        }
+
+        return suggestions.join("\n")
+    }
+
+    public getExampleFix(): string {
+        if (this.props.fromLayer === "domain" && this.props.toLayer === "infrastructure") {
+            return `
+// ❌ Bad: Domain depends on Infrastructure (PrismaClient)
+// domain/services/UserService.ts
+class UserService {
+    constructor(private prisma: PrismaClient) {}
+}
+
+// ✅ Good: Domain defines interface, Infrastructure implements
+// domain/repositories/IUserRepository.ts
+interface IUserRepository {
+    findById(id: UserId): Promise<User | null>
+    save(user: User): Promise<void>
+}
+
+// domain/services/UserService.ts
+class UserService {
+    constructor(private userRepo: IUserRepository) {}
+}
+
+// infrastructure/repositories/PrismaUserRepository.ts
+class PrismaUserRepository implements IUserRepository {
+    constructor(private prisma: PrismaClient) {}
+    async findById(id: UserId): Promise<User | null> { }
+    async save(user: User): Promise<void> { }
+}`
+        }
+
+        if (this.props.fromLayer === "application" && this.props.toLayer === "infrastructure") {
+            return `
+// ❌ Bad: Application depends on Infrastructure (SmtpEmailService)
+// application/use-cases/SendEmail.ts
+class SendWelcomeEmail {
+    constructor(private emailService: SmtpEmailService) {}
+}
+
+// ✅ Good: Application defines Port, Infrastructure implements Adapter
+// application/ports/IEmailService.ts
+interface IEmailService {
+    send(to: string, subject: string, body: string): Promise<void>
+}
+
+// application/use-cases/SendEmail.ts
+class SendWelcomeEmail {
+    constructor(private emailService: IEmailService) {}
+}
+
+// infrastructure/adapters/SmtpEmailService.ts
+class SmtpEmailService implements IEmailService {
+    async send(to: string, subject: string, body: string): Promise<void> { }
+}`
+        }
+
+        return ""
+    }
+
+    private capitalizeFirst(str: string): string {
+        return str.charAt(0).toUpperCase() + str.slice(1)
+    }
+}

packages/guardian/src/infrastructure/analyzers/DependencyDirectionDetector.ts

@@ -0,0 +1,183 @@
+import { IDependencyDirectionDetector } from "../../domain/services/IDependencyDirectionDetector"
+import { DependencyViolation } from "../../domain/value-objects/DependencyViolation"
+import { LAYERS } from "../../shared/constants/rules"
+
+/**
+ * Detects dependency direction violations between architectural layers
+ *
+ * This detector enforces Clean Architecture dependency rules:
+ * - Domain → should not import from Application or Infrastructure
+ * - Application → should not import from Infrastructure
+ * - Infrastructure → can import from Application and Domain (allowed)
+ * - Shared → can be imported by all layers (allowed)
+ *
+ * @example
+ * ```typescript
+ * const detector = new DependencyDirectionDetector()
+ *
+ * // Detect violations in domain file
+ * const code = `
+ * import { PrismaClient } from '@prisma/client'
+ * import { UserDto } from '../application/dtos/UserDto'
+ * `
+ * const violations = detector.detectViolations(code, 'src/domain/entities/User.ts', 'domain')
+ *
+ * // violations will contain 1 violation for domain importing from application
+ * console.log(violations.length) // 1
+ * console.log(violations[0].getMessage())
+ * // "Domain layer should not import from Application layer"
+ * ```
+ */
+export class DependencyDirectionDetector implements IDependencyDirectionDetector {
+    private readonly dependencyRules: Map<string, Set<string>>
+
+    constructor() {
+        this.dependencyRules = new Map([
+            [LAYERS.DOMAIN, new Set([LAYERS.DOMAIN, LAYERS.SHARED])],
+            [LAYERS.APPLICATION, new Set([LAYERS.DOMAIN, LAYERS.APPLICATION, LAYERS.SHARED])],
+            [
+                LAYERS.INFRASTRUCTURE,
+                new Set([LAYERS.DOMAIN, LAYERS.APPLICATION, LAYERS.INFRASTRUCTURE, LAYERS.SHARED]),
+            ],
+            [
+                LAYERS.SHARED,
+                new Set([LAYERS.DOMAIN, LAYERS.APPLICATION, LAYERS.INFRASTRUCTURE, LAYERS.SHARED]),
+            ],
+        ])
+    }
+
+    /**
+     * Detects dependency direction violations in the given code
+     *
+     * Analyzes import statements to identify violations of dependency rules
+     * between architectural layers.
+     *
+     * @param code - Source code to analyze
+     * @param filePath - Path to the file being analyzed
+     * @param layer - The architectural layer of the file (domain, application, infrastructure, shared)
+     * @returns Array of detected dependency direction violations
+     */
+    public detectViolations(
+        code: string,
+        filePath: string,
+        layer: string | undefined,
+    ): DependencyViolation[] {
+        if (!layer || layer === LAYERS.SHARED) {
+            return []
+        }
+
+        const violations: DependencyViolation[] = []
+        const lines = code.split("\n")
+
+        for (let i = 0; i < lines.length; i++) {
+            const line = lines[i]
+            const lineNumber = i + 1
+
+            const imports = this.extractImports(line)
+            for (const importPath of imports) {
+                const targetLayer = this.extractLayerFromImport(importPath)
+
+                if (targetLayer && this.isViolation(layer, targetLayer)) {
+                    violations.push(
+                        DependencyViolation.create(
+                            layer,
+                            targetLayer,
+                            importPath,
+                            filePath,
+                            lineNumber,
+                        ),
+                    )
+                }
+            }
+        }
+
+        return violations
+    }
+
+    /**
+     * Checks if an import violates dependency direction rules
+     *
+     * @param fromLayer - The layer that is importing
+     * @param toLayer - The layer being imported
+     * @returns True if the import violates dependency rules
+     */
+    public isViolation(fromLayer: string, toLayer: string): boolean {
+        const allowedDependencies = this.dependencyRules.get(fromLayer)
+
+        if (!allowedDependencies) {
+            return false
+        }
+
+        return !allowedDependencies.has(toLayer)
+    }
+
+    /**
+     * Extracts the layer from an import path
+     *
+     * @param importPath - The import path to analyze
+     * @returns The layer name if detected, undefined otherwise
+     */
+    public extractLayerFromImport(importPath: string): string | undefined {
+        const normalizedPath = importPath.replace(/['"]/g, "").toLowerCase()
+
+        const layerPatterns: Array<[string, string]> = [
+            [LAYERS.DOMAIN, "/domain/"],
+            [LAYERS.APPLICATION, "/application/"],
+            [LAYERS.INFRASTRUCTURE, "/infrastructure/"],
+            [LAYERS.SHARED, "/shared/"],
+        ]
+
+        for (const [layer, pattern] of layerPatterns) {
+            if (this.containsLayerPattern(normalizedPath, pattern)) {
+                return layer
+            }
+        }
+
+        return undefined
+    }
+
+    /**
+     * Checks if the normalized path contains the layer pattern
+     */
+    private containsLayerPattern(normalizedPath: string, pattern: string): boolean {
+        return (
+            normalizedPath.includes(pattern) ||
+            normalizedPath.includes(`.${pattern}`) ||
+            normalizedPath.includes(`..${pattern}`) ||
+            normalizedPath.includes(`...${pattern}`)
+        )
+    }
+
+    /**
+     * Extracts import paths from a line of code
+     *
+     * Handles various import statement formats:
+     * - import { X } from 'path'
+     * - import X from 'path'
+     * - import * as X from 'path'
+     * - const X = require('path')
+     *
+     * @param line - A line of code to analyze
+     * @returns Array of import paths found in the line
+     */
+    private extractImports(line: string): string[] {
+        const imports: string[] = []
+
+        const esImportRegex =
+            /import\s+(?:{[^}]*}|[\w*]+(?:\s+as\s+\w+)?|\*\s+as\s+\w+)\s+from\s+['"]([^'"]+)['"]/g
+        let match = esImportRegex.exec(line)
+        while (match) {
+            imports.push(match[1])
+            match = esImportRegex.exec(line)
+        }
+
+        const requireRegex = /require\s*\(\s*['"]([^'"]+)['"]\s*\)/g
+        match = requireRegex.exec(line)
+        while (match) {
+            imports.push(match[1])
+            match = requireRegex.exec(line)
+        }
+
+        return imports
+    }
+}

packages/guardian/src/shared/constants/rules.ts

@@ -8,6 +8,7 @@ export const RULES = {
     NAMING_CONVENTION: "naming-convention",
     FRAMEWORK_LEAK: "framework-leak",
     ENTITY_EXPOSURE: "entity-exposure",
+    DEPENDENCY_DIRECTION: "dependency-direction",
 } as const
 
 /**

packages/guardian/tests/DependencyDirectionDetector.test.ts

@@ -0,0 +1,511 @@
+import { describe, it, expect } from "vitest"
+import { DependencyDirectionDetector } from "../src/infrastructure/analyzers/DependencyDirectionDetector"
+import { LAYERS } from "../src/shared/constants/rules"
+
+describe("DependencyDirectionDetector", () => {
+    const detector = new DependencyDirectionDetector()
+
+    describe("extractLayerFromImport", () => {
+        it("should extract domain layer from import path", () => {
+            expect(detector.extractLayerFromImport("../domain/entities/User")).toBe(LAYERS.DOMAIN)
+            expect(detector.extractLayerFromImport("../../domain/value-objects/Email")).toBe(
+                LAYERS.DOMAIN,
+            )
+            expect(detector.extractLayerFromImport("../../../domain/services/UserService")).toBe(
+                LAYERS.DOMAIN,
+            )
+        })
+
+        it("should extract application layer from import path", () => {
+            expect(detector.extractLayerFromImport("../application/use-cases/CreateUser")).toBe(
+                LAYERS.APPLICATION,
+            )
+            expect(detector.extractLayerFromImport("../../application/dtos/UserDto")).toBe(
+                LAYERS.APPLICATION,
+            )
+            expect(detector.extractLayerFromImport("../../../application/mappers/UserMapper")).toBe(
+                LAYERS.APPLICATION,
+            )
+        })
+
+        it("should extract infrastructure layer from import path", () => {
+            expect(
+                detector.extractLayerFromImport("../infrastructure/controllers/UserController"),
+            ).toBe(LAYERS.INFRASTRUCTURE)
+            expect(
+                detector.extractLayerFromImport("../../infrastructure/repositories/UserRepository"),
+            ).toBe(LAYERS.INFRASTRUCTURE)
+        })
+
+        it("should extract shared layer from import path", () => {
+            expect(detector.extractLayerFromImport("../shared/types/Result")).toBe(LAYERS.SHARED)
+            expect(detector.extractLayerFromImport("../../shared/constants/rules")).toBe(
+                LAYERS.SHARED,
+            )
+        })
+
+        it("should return undefined for non-layer imports", () => {
+            expect(detector.extractLayerFromImport("express")).toBeUndefined()
+            expect(detector.extractLayerFromImport("../utils/helper")).toBeUndefined()
+            expect(detector.extractLayerFromImport("../../lib/logger")).toBeUndefined()
+        })
+    })
+
+    describe("isViolation", () => {
+        it("should allow domain to import from domain", () => {
+            expect(detector.isViolation(LAYERS.DOMAIN, LAYERS.DOMAIN)).toBe(false)
+        })
+
+        it("should allow domain to import from shared", () => {
+            expect(detector.isViolation(LAYERS.DOMAIN, LAYERS.SHARED)).toBe(false)
+        })
+
+        it("should NOT allow domain to import from application", () => {
+            expect(detector.isViolation(LAYERS.DOMAIN, LAYERS.APPLICATION)).toBe(true)
+        })
+
+        it("should NOT allow domain to import from infrastructure", () => {
+            expect(detector.isViolation(LAYERS.DOMAIN, LAYERS.INFRASTRUCTURE)).toBe(true)
+        })
+
+        it("should allow application to import from domain", () => {
+            expect(detector.isViolation(LAYERS.APPLICATION, LAYERS.DOMAIN)).toBe(false)
+        })
+
+        it("should allow application to import from application", () => {
+            expect(detector.isViolation(LAYERS.APPLICATION, LAYERS.APPLICATION)).toBe(false)
+        })
+
+        it("should allow application to import from shared", () => {
+            expect(detector.isViolation(LAYERS.APPLICATION, LAYERS.SHARED)).toBe(false)
+        })
+
+        it("should NOT allow application to import from infrastructure", () => {
+            expect(detector.isViolation(LAYERS.APPLICATION, LAYERS.INFRASTRUCTURE)).toBe(true)
+        })
+
+        it("should allow infrastructure to import from domain", () => {
+            expect(detector.isViolation(LAYERS.INFRASTRUCTURE, LAYERS.DOMAIN)).toBe(false)
+        })
+
+        it("should allow infrastructure to import from application", () => {
+            expect(detector.isViolation(LAYERS.INFRASTRUCTURE, LAYERS.APPLICATION)).toBe(false)
+        })
+
+        it("should allow infrastructure to import from infrastructure", () => {
+            expect(detector.isViolation(LAYERS.INFRASTRUCTURE, LAYERS.INFRASTRUCTURE)).toBe(false)
+        })
+
+        it("should allow infrastructure to import from shared", () => {
+            expect(detector.isViolation(LAYERS.INFRASTRUCTURE, LAYERS.SHARED)).toBe(false)
+        })
+
+        it("should allow shared to import from any layer", () => {
+            expect(detector.isViolation(LAYERS.SHARED, LAYERS.DOMAIN)).toBe(false)
+            expect(detector.isViolation(LAYERS.SHARED, LAYERS.APPLICATION)).toBe(false)
+            expect(detector.isViolation(LAYERS.SHARED, LAYERS.INFRASTRUCTURE)).toBe(false)
+            expect(detector.isViolation(LAYERS.SHARED, LAYERS.SHARED)).toBe(false)
+        })
+    })
+
+    describe("detectViolations", () => {
+        describe("Domain layer violations", () => {
+            it("should detect domain importing from application", () => {
+                const code = `
+import { UserDto } from '../../application/dtos/UserDto'
+
+export class User {
+    constructor(private id: string) {}
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(1)
+                expect(violations[0].fromLayer).toBe(LAYERS.DOMAIN)
+                expect(violations[0].toLayer).toBe(LAYERS.APPLICATION)
+                expect(violations[0].importPath).toBe("../../application/dtos/UserDto")
+                expect(violations[0].line).toBe(2)
+            })
+
+            it("should detect domain importing from infrastructure", () => {
+                const code = `
+import { PrismaClient } from '../../infrastructure/database/PrismaClient'
+
+export class UserRepository {
+    constructor(private prisma: PrismaClient) {}
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/repositories/UserRepository.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(1)
+                expect(violations[0].fromLayer).toBe(LAYERS.DOMAIN)
+                expect(violations[0].toLayer).toBe(LAYERS.INFRASTRUCTURE)
+                expect(violations[0].importPath).toBe("../../infrastructure/database/PrismaClient")
+            })
+
+            it("should NOT detect domain importing from domain", () => {
+                const code = `
+import { Email } from '../value-objects/Email'
+import { UserId } from '../value-objects/UserId'
+
+export class User {
+    constructor(
+        private id: UserId,
+        private email: Email
+    ) {}
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+
+            it("should NOT detect domain importing from shared", () => {
+                const code = `
+import { Result } from '../../shared/types/Result'
+
+export class User {
+    static create(id: string): Result<User> {
+        return Result.ok(new User(id))
+    }
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+        })
+
+        describe("Application layer violations", () => {
+            it("should detect application importing from infrastructure", () => {
+                const code = `
+import { SmtpEmailService } from '../../infrastructure/email/SmtpEmailService'
+
+export class SendWelcomeEmail {
+    constructor(private emailService: SmtpEmailService) {}
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/application/use-cases/SendWelcomeEmail.ts",
+                    LAYERS.APPLICATION,
+                )
+
+                expect(violations).toHaveLength(1)
+                expect(violations[0].fromLayer).toBe(LAYERS.APPLICATION)
+                expect(violations[0].toLayer).toBe(LAYERS.INFRASTRUCTURE)
+                expect(violations[0].getMessage()).toContain(
+                    "Application layer should not import from Infrastructure layer",
+                )
+            })
+
+            it("should NOT detect application importing from domain", () => {
+                const code = `
+import { User } from '../../domain/entities/User'
+import { IUserRepository } from '../../domain/repositories/IUserRepository'
+
+export class CreateUser {
+    constructor(private userRepo: IUserRepository) {}
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/application/use-cases/CreateUser.ts",
+                    LAYERS.APPLICATION,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+
+            it("should NOT detect application importing from application", () => {
+                const code = `
+import { UserResponseDto } from '../dtos/UserResponseDto'
+import { UserMapper } from '../mappers/UserMapper'
+
+export class GetUser {
+    execute(id: string): UserResponseDto {
+        return UserMapper.toDto(user)
+    }
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/application/use-cases/GetUser.ts",
+                    LAYERS.APPLICATION,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+
+            it("should NOT detect application importing from shared", () => {
+                const code = `
+import { Result } from '../../shared/types/Result'
+
+export class CreateUser {
+    execute(): Result<User> {
+        return Result.ok(user)
+    }
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/application/use-cases/CreateUser.ts",
+                    LAYERS.APPLICATION,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+        })
+
+        describe("Infrastructure layer", () => {
+            it("should NOT detect infrastructure importing from domain", () => {
+                const code = `
+import { User } from '../../domain/entities/User'
+import { IUserRepository } from '../../domain/repositories/IUserRepository'
+
+export class PrismaUserRepository implements IUserRepository {
+    async save(user: User): Promise<void> {}
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/infrastructure/repositories/PrismaUserRepository.ts",
+                    LAYERS.INFRASTRUCTURE,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+
+            it("should NOT detect infrastructure importing from application", () => {
+                const code = `
+import { CreateUser } from '../../application/use-cases/CreateUser'
+import { UserResponseDto } from '../../application/dtos/UserResponseDto'
+
+export class UserController {
+    constructor(private createUser: CreateUser) {}
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/infrastructure/controllers/UserController.ts",
+                    LAYERS.INFRASTRUCTURE,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+
+            it("should NOT detect infrastructure importing from infrastructure", () => {
+                const code = `
+import { DatabaseConnection } from '../database/DatabaseConnection'
+
+export class PrismaUserRepository {
+    constructor(private db: DatabaseConnection) {}
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/infrastructure/repositories/PrismaUserRepository.ts",
+                    LAYERS.INFRASTRUCTURE,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+        })
+
+        describe("Multiple violations", () => {
+            it("should detect multiple violations in same file", () => {
+                const code = `
+import { UserDto } from '../../application/dtos/UserDto'
+import { EmailService } from '../../infrastructure/email/EmailService'
+import { Logger } from '../../infrastructure/logging/Logger'
+
+export class User {
+    constructor() {}
+}`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(3)
+                expect(violations[0].toLayer).toBe(LAYERS.APPLICATION)
+                expect(violations[1].toLayer).toBe(LAYERS.INFRASTRUCTURE)
+                expect(violations[2].toLayer).toBe(LAYERS.INFRASTRUCTURE)
+            })
+        })
+
+        describe("Import statement formats", () => {
+            it("should detect violations in named imports", () => {
+                const code = `import { UserDto, UserRequest } from '../../application/dtos/UserDto'`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(1)
+            })
+
+            it("should detect violations in default imports", () => {
+                const code = `import UserDto from '../../application/dtos/UserDto'`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(1)
+            })
+
+            it("should detect violations in namespace imports", () => {
+                const code = `import * as Dtos from '../../application/dtos'`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(1)
+            })
+
+            it("should detect violations in require statements", () => {
+                const code = `const UserDto = require('../../application/dtos/UserDto')`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(1)
+            })
+        })
+
+        describe("Edge cases", () => {
+            it("should return empty array for shared layer", () => {
+                const code = `
+import { User } from '../../domain/entities/User'
+import { CreateUser } from '../../application/use-cases/CreateUser'
+`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/shared/types/Result.ts",
+                    LAYERS.SHARED,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+
+            it("should return empty array for undefined layer", () => {
+                const code = `import { UserDto } from '../../application/dtos/UserDto'`
+                const violations = detector.detectViolations(code, "src/utils/helper.ts", undefined)
+
+                expect(violations).toHaveLength(0)
+            })
+
+            it("should handle empty code", () => {
+                const violations = detector.detectViolations(
+                    "",
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations).toHaveLength(0)
+            })
+        })
+
+        describe("getMessage", () => {
+            it("should return correct message for domain -> application violation", () => {
+                const code = `import { UserDto } from '../../application/dtos/UserDto'`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/entities/User.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                expect(violations[0].getMessage()).toBe(
+                    "Domain layer should not import from Application layer",
+                )
+            })
+
+            it("should return correct message for application -> infrastructure violation", () => {
+                const code = `import { SmtpEmailService } from '../../infrastructure/email/SmtpEmailService'`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/application/use-cases/SendEmail.ts",
+                    LAYERS.APPLICATION,
+                )
+
+                expect(violations[0].getMessage()).toBe(
+                    "Application layer should not import from Infrastructure layer",
+                )
+            })
+        })
+
+        describe("getSuggestion", () => {
+            it("should return suggestions for domain layer violations", () => {
+                const code = `import { PrismaClient } from '../../infrastructure/database'`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/services/UserService.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                const suggestion = violations[0].getSuggestion()
+                expect(suggestion).toContain("Domain layer should be independent")
+                expect(suggestion).toContain("dependency inversion")
+            })
+
+            it("should return suggestions for application layer violations", () => {
+                const code = `import { SmtpEmailService } from '../../infrastructure/email/SmtpEmailService'`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/application/use-cases/SendEmail.ts",
+                    LAYERS.APPLICATION,
+                )
+
+                const suggestion = violations[0].getSuggestion()
+                expect(suggestion).toContain(
+                    "Application layer should not depend on infrastructure",
+                )
+                expect(suggestion).toContain("Port")
+                expect(suggestion).toContain("Adapter")
+            })
+        })
+
+        describe("getExampleFix", () => {
+            it("should return example fix for domain -> infrastructure violation", () => {
+                const code = `import { PrismaClient } from '../../infrastructure/database'`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/domain/services/UserService.ts",
+                    LAYERS.DOMAIN,
+                )
+
+                const example = violations[0].getExampleFix()
+                expect(example).toContain("// ❌ Bad")
+                expect(example).toContain("// ✅ Good")
+                expect(example).toContain("IUserRepository")
+            })
+
+            it("should return example fix for application -> infrastructure violation", () => {
+                const code = `import { SmtpEmailService } from '../../infrastructure/email/SmtpEmailService'`
+                const violations = detector.detectViolations(
+                    code,
+                    "src/application/use-cases/SendEmail.ts",
+                    LAYERS.APPLICATION,
+                )
+
+                const example = violations[0].getExampleFix()
+                expect(example).toContain("// ❌ Bad")
+                expect(example).toContain("// ✅ Good")
+                expect(example).toContain("IEmailService")
+            })
+        })
+    })
+})