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

Template

<?php

declare(strict_types=1);

namespace Domain\{BoundedContext}\Entity;

use Domain\{BoundedContext}\ValueObject\{Name}Id;
use Domain\{BoundedContext}\Enum\{Name}Status;
use Domain\{BoundedContext}\Exception\{Exceptions};

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 Template

<?php

declare(strict_types=1);

namespace Tests\Unit\Domain\{BoundedContext}\Entity;

use Domain\{BoundedContext}\Entity\{Name};
use Domain\{BoundedContext}\ValueObject\{Name}Id;
use Domain\{BoundedContext}\Enum\{Name}Status;
use PHPUnit\Framework\Attributes\CoversClass;
use PHPUnit\Framework\Attributes\Group;
use PHPUnit\Framework\TestCase;

#[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}
        );
    }
}

Common Entity Patterns

Order Entity

<?php

declare(strict_types=1);

namespace Domain\Order\Entity;

use Domain\Order\ValueObject\OrderId;
use Domain\Order\ValueObject\CustomerId;
use Domain\Order\ValueObject\Money;
use Domain\Order\Enum\OrderStatus;
use Domain\Order\Exception\CannotModifyConfirmedOrderException;
use Domain\Order\Exception\CannotConfirmEmptyOrderException;
use Domain\Order\Exception\InvalidStateTransitionException;

final class Order
{
    private OrderStatus $status;
    /** @var array<OrderLine> */
    private array $lines = [];
    private DateTimeImmutable $createdAt;
    private ?DateTimeImmutable $confirmedAt = null;

    public function __construct(
        private readonly OrderId $id,
        private readonly CustomerId $customerId
    ) {
        $this->status = OrderStatus::Draft;
        $this->createdAt = new DateTimeImmutable();
    }

    public function id(): OrderId
    {
        return $this->id;
    }

    public function customerId(): CustomerId
    {
        return $this->customerId;
    }

    public function status(): OrderStatus
    {
        return $this->status;
    }

    public function addLine(Product $product, int $quantity): void
    {
        if ($this->status !== OrderStatus::Draft) {
            throw new CannotModifyConfirmedOrderException($this->id);
        }

        $this->lines[] = new OrderLine(
            product: $product,
            quantity: $quantity,
            unitPrice: $product->price()
        );
    }

    public function removeLine(int $index): void
    {
        if ($this->status !== OrderStatus::Draft) {
            throw new CannotModifyConfirmedOrderException($this->id);
        }

        if (!isset($this->lines[$index])) {
            return;
        }

        unset($this->lines[$index]);
        $this->lines = array_values($this->lines);
    }

    public function confirm(): void
    {
        if ($this->status !== OrderStatus::Draft) {
            throw new InvalidStateTransitionException(
                $this->status,
                OrderStatus::Confirmed
            );
        }

        if (empty($this->lines)) {
            throw new CannotConfirmEmptyOrderException($this->id);
        }

        $this->status = OrderStatus::Confirmed;
        $this->confirmedAt = new DateTimeImmutable();
    }

    public function cancel(): void
    {
        if (!$this->status->canBeCancelled()) {
            throw new InvalidStateTransitionException(
                $this->status,
                OrderStatus::Cancelled
            );
        }

        $this->status = OrderStatus::Cancelled;
    }

    public function total(): Money
    {
        return array_reduce(
            $this->lines,
            fn (Money $carry, OrderLine $line) => $carry->add($line->total()),
            Money::zero('USD')
        );
    }

    /**
     * @return array<OrderLine>
     */
    public function lines(): array
    {
        return $this->lines;
    }

    public function lineCount(): int
    {
        return count($this->lines);
    }

    public function isEmpty(): bool
    {
        return empty($this->lines);
    }

    public function createdAt(): DateTimeImmutable
    {
        return $this->createdAt;
    }

    public function confirmedAt(): ?DateTimeImmutable
    {
        return $this->confirmedAt;
    }
}

User Entity

<?php

declare(strict_types=1);

namespace Domain\User\Entity;

use Domain\User\ValueObject\UserId;
use Domain\User\ValueObject\Email;
use Domain\User\ValueObject\HashedPassword;
use Domain\User\Enum\UserStatus;
use Domain\User\Exception\UserAlreadyActivatedException;
use Domain\User\Exception\UserDeactivatedException;

final class User
{
    private UserStatus $status;
    private DateTimeImmutable $createdAt;
    private ?DateTimeImmutable $lastLoginAt = null;

    public function __construct(
        private readonly UserId $id,
        private Email $email,
        private HashedPassword $password,
        private string $name
    ) {
        if (empty(trim($name))) {
            throw new InvalidUserNameException();
        }

        $this->status = UserStatus::Pending;
        $this->createdAt = new DateTimeImmutable();
    }

    public function id(): UserId
    {
        return $this->id;
    }

    public function email(): Email
    {
        return $this->email;
    }

    public function name(): string
    {
        return $this->name;
    }

    public function status(): UserStatus
    {
        return $this->status;
    }

    public function activate(): void
    {
        if ($this->status === UserStatus::Active) {
            throw new UserAlreadyActivatedException($this->id);
        }

        $this->status = UserStatus::Active;
    }

    public function deactivate(): void
    {
        $this->status = UserStatus::Deactivated;
    }

    public function changeEmail(Email $newEmail): void
    {
        $this->ensureActive();
        $this->email = $newEmail;
    }

    public function changePassword(HashedPassword $newPassword): void
    {
        $this->ensureActive();
        $this->password = $newPassword;
    }

    public function changeName(string $newName): void
    {
        $this->ensureActive();

        if (empty(trim($newName))) {
            throw new InvalidUserNameException();
        }

        $this->name = $newName;
    }

    public function recordLogin(): void
    {
        $this->ensureActive();
        $this->lastLoginAt = new DateTimeImmutable();
    }

    public function verifyPassword(string $plainPassword, PasswordHasherInterface $hasher): bool
    {
        return $hasher->verify($this->password, $plainPassword);
    }

    public function isActive(): bool
    {
        return $this->status === UserStatus::Active;
    }

    private function ensureActive(): void
    {
        if ($this->status === UserStatus::Deactivated) {
            throw new UserDeactivatedException($this->id);
        }
    }
}

Entity Design Principles

1. Behavior Over Data

// BAD: Anemic entity
class Order
{
    public function setStatus(string $status): void
    {
        $this->status = $status;
    }
}

// GOOD: Rich entity with behavior
class Order
{
    public function confirm(): void
    {
        if (!$this->canBeConfirmed()) {
            throw new InvalidStateTransitionException();
        }
        $this->status = OrderStatus::Confirmed;
        $this->confirmedAt = new DateTimeImmutable();
    }

    private function canBeConfirmed(): bool
    {
        return $this->status === OrderStatus::Draft && !empty($this->lines);
    }
}

2. Invariant Protection

// Protect invariants in every method
public function addLine(Product $product, int $quantity): void
{
    // Invariant: Can only modify draft orders
    if ($this->status !== OrderStatus::Draft) {
        throw new CannotModifyConfirmedOrderException();
    }

    // Invariant: Quantity must be positive
    if ($quantity <= 0) {
        throw new InvalidQuantityException();
    }

    $this->lines[] = new OrderLine($product, $quantity);
}

3. State Transitions

enum OrderStatus: string
{
    case Draft = 'draft';
    case Confirmed = 'confirmed';
    case Paid = 'paid';
    case Shipped = 'shipped';
    case Cancelled = 'cancelled';

    public function canTransitionTo(self $target): bool
    {
        return match($this) {
            self::Draft => in_array($target, [self::Confirmed, self::Cancelled]),
            self::Confirmed => in_array($target, [self::Paid, self::Cancelled]),
            self::Paid => in_array($target, [self::Shipped, self::Cancelled]),
            self::Shipped => false,
            self::Cancelled => false,
        };
    }

    public function canBeCancelled(): bool
    {
        return $this->canTransitionTo(self::Cancelled);
    }
}

Generation Instructions

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)

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