Entity Generator

Generate DDD-compliant Entities with identity, behavior, and tests.

Entity Characteristics

• Identity: Has unique identifier (ID)
• Lifecycle: Created, modified, potentially deleted
• Behavior: Contains domain logic (not just data)
• Invariants: Protects business rules
• State transitions: Controlled mutations
• No public setters: State changed via behavior methods

Entity Components

Core Structure

Every Entity consists of:

Component	Description
Identity ({Name}Id)	Unique identifier, readonly, set at construction
Status Enum	Lifecycle states with transition rules
Constructor	Sets identity, initial status, timestamps, validates invariants
Behavior methods	Domain actions (confirm(), cancel(), addLine())
Query methods	State checks (isActive(), canBeConfirmed(), isEmpty())
touch() helper	Updates $updatedAt timestamp on mutations

Supporting Files

File	Location
Entity	src/Domain/{BoundedContext}/Entity/{Name}.php
Status Enum	src/Domain/{BoundedContext}/Enum/{Name}Status.php
Exceptions	src/Domain/{BoundedContext}/Exception/{...}Exception.php
Unit Test	tests/Unit/Domain/{BoundedContext}/Entity/{Name}Test.php

Entity Design Principles

1. Behavior Over Data

Entities must encapsulate domain logic, not just hold data. Use meaningful behavior methods (confirm(), activate()) instead of anemic setters (setStatus()). Each behavior method enforces invariants before mutating state.

2. Invariant Protection

Every mutation method must validate business rules before making changes. Common invariants:

• State guards (e.g., can only modify draft orders)
• Value constraints (e.g., quantity must be positive)
• Relationship constraints (e.g., cannot confirm empty order)

3. State Transitions

Use a Status enum with explicit transition rules. The enum defines canTransitionTo() to enforce valid state machines. Entities delegate transition validation to the enum.

Generation Process

When asked to create an Entity:

1. Identify the identity (what makes it unique)
2. Define the lifecycle (statuses/states)
3. List invariants (business rules to protect)
4. Design behavior methods (what it can do)
5. Generate tests for behavior and invariants

Naming Conventions

Concept	Method Pattern	Exception
State change	confirm(), activate(), cancel()	InvalidStateTransitionException
Add relation	addLine(), addItem()	CannotModifyException
Update property	changeEmail(), updateName()	InvalidValueException
Query state	isActive(), canBeConfirmed()	N/A (boolean return)

Quick Template Reference

Entity skeleton

final class {Name}
{
    private {Name}Status $status;
    private DateTimeImmutable $createdAt;
    private ?DateTimeImmutable $updatedAt = null;

    public function __construct(
        private readonly {Name}Id $id,
        {constructorProperties}
    ) {
        {constructorValidation}
        $this->status = {Name}Status::default();
        $this->createdAt = new DateTimeImmutable();
    }

    public function id(): {Name}Id { return $this->id; }
    public function status(): {Name}Status { return $this->status; }

    {behaviorMethods}

    private function touch(): void { $this->updatedAt = new DateTimeImmutable(); }
}

Test skeleton

#[Group('unit')]
#[CoversClass({Name}::class)]
final class {Name}Test extends TestCase
{
    public function testCreatesWithValidData(): void
    {
        $entity = $this->createEntity();
        self::assertInstanceOf({Name}Id::class, $entity->id());
        self::assertSame({Name}Status::default(), $entity->status());
    }

    {behaviorTests}

    private function createEntity(): {Name}
    {
        return new {Name}(id: {Name}Id::generate(), {testConstructorArgs});
    }
}

Usage

To generate an Entity, provide:

• Name (e.g., "Order", "User")
• Bounded Context (e.g., "Order", "User")
• Identity type (e.g., "OrderId")
• States/Statuses
• Key behaviors needed
• Invariants to protect

References

• references/templates.md — full PHP code templates (Entity, Test, State Transition Enum, design principle code samples)
• references/examples.md — complete Order Entity and User Entity implementation examples