diff --git a/src/Contracts/AssigneeManagerInterface.php b/src/Contracts/AssigneeManagerInterface.php
new file mode 100644
index 0000000..b51783f
--- /dev/null
+++ b/src/Contracts/AssigneeManagerInterface.php
@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Contracts;
+
+use Illuminate\Support\Collection;
+
+interface AssigneeManagerInterface
+{
+    /**
+     * Get all assignees for the pull request.
+     *
+     * @return Collection<int, \ConduitUI\Pr\DataTransferObjects\User>
+     */
+    public function get(): Collection;
+
+    /**
+     * Add a single assignee.
+     */
+    public function add(string $username): self;
+
+    /**
+     * Add multiple assignees.
+     *
+     * @param  array<int, string>  $usernames
+     */
+    public function addMany(array $usernames): self;
+
+    /**
+     * Remove a single assignee.
+     */
+    public function remove(string $username): self;
+
+    /**
+     * Remove multiple assignees.
+     *
+     * @param  array<int, string>  $usernames
+     */
+    public function removeMany(array $usernames): self;
+
+    /**
+     * Replace all assignees with new ones.
+     *
+     * @param  array<int, string>  $usernames
+     */
+    public function replace(array $usernames): self;
+
+    /**
+     * Clear all assignees.
+     */
+    public function clear(): self;
+
+    /**
+     * Check if a user is assigned.
+     */
+    public function has(string $username): bool;
+}
diff --git a/src/DataTransferObjects/Milestone.php b/src/DataTransferObjects/Milestone.php
new file mode 100644
index 0000000..51fe5b3
--- /dev/null
+++ b/src/DataTransferObjects/Milestone.php
@@ -0,0 +1,92 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\DataTransferObjects;
+
+use Carbon\Carbon;
+
+class Milestone
+{
+    public function __construct(
+        public readonly int $number,
+        public readonly string $title,
+        public readonly ?string $description,
+        public readonly string $state,
+        public readonly int $openIssues,
+        public readonly int $closedIssues,
+        public readonly ?Carbon $dueOn,
+        public readonly Carbon $createdAt,
+        public readonly Carbon $updatedAt,
+        public readonly ?Carbon $closedAt,
+        public readonly string $htmlUrl,
+    ) {}
+
+    /**
+     * @param  array<string, mixed>  $data
+     */
+    public static function fromArray(array $data): self
+    {
+        return new self(
+            number: $data['number'],
+            title: $data['title'],
+            description: $data['description'] ?? null,
+            state: $data['state'],
+            openIssues: $data['open_issues'],
+            closedIssues: $data['closed_issues'],
+            dueOn: isset($data['due_on']) ? Carbon::parse($data['due_on']) : null,
+            createdAt: Carbon::parse($data['created_at']),
+            updatedAt: Carbon::parse($data['updated_at']),
+            closedAt: isset($data['closed_at']) ? Carbon::parse($data['closed_at']) : null,
+            htmlUrl: $data['html_url'],
+        );
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    public function toArray(): array
+    {
+        return [
+            'number' => $this->number,
+            'title' => $this->title,
+            'description' => $this->description,
+            'state' => $this->state,
+            'open_issues' => $this->openIssues,
+            'closed_issues' => $this->closedIssues,
+            'due_on' => $this->dueOn?->toIso8601String(),
+            'created_at' => $this->createdAt->toIso8601String(),
+            'updated_at' => $this->updatedAt->toIso8601String(),
+            'closed_at' => $this->closedAt?->toIso8601String(),
+            'html_url' => $this->htmlUrl,
+        ];
+    }
+
+    public function isOpen(): bool
+    {
+        return $this->state === 'open';
+    }
+
+    public function isClosed(): bool
+    {
+        return $this->state === 'closed';
+    }
+
+    public function isOverdue(): bool
+    {
+        return $this->dueOn !== null
+            && $this->dueOn->isPast()
+            && $this->isOpen();
+    }
+
+    public function progress(): float
+    {
+        $total = $this->openIssues + $this->closedIssues;
+
+        if ($total === 0) {
+            return 0.0;
+        }
+
+        return round(($this->closedIssues / $total) * 100, 2);
+    }
+}
diff --git a/src/PullRequest.php b/src/PullRequest.php
index b4172e9..986877b 100644
--- a/src/PullRequest.php
+++ b/src/PullRequest.php
@@ -39,6 +39,8 @@
 use ConduitUI\Pr\Requests\RemoveReviewers;
 use ConduitUI\Pr\Requests\RequestReviewers;
 use ConduitUI\Pr\Requests\UpdatePullRequest;
+use ConduitUI\Pr\Services\AssigneeManager;
+use ConduitUI\Pr\Services\MilestoneManager;
 use ConduitUI\Pr\Services\ReviewBuilder;
 use ConduitUI\Pr\Services\ReviewQuery;
 
@@ -471,6 +473,32 @@ public function timeline(): array
         return $allEvents;
     }
 
+    /**
+     * Get an assignee manager for this pull request.
+     */
+    public function assignees(): AssigneeManager
+    {
+        return new AssigneeManager($this->connector, "{$this->owner}/{$this->repo}", $this->data->number);
+    }
+
+    /**
+     * Get a milestone manager for this pull request.
+     */
+    public function milestone(): MilestoneManager
+    {
+        return new MilestoneManager($this->connector, "{$this->owner}/{$this->repo}", $this->data->number);
+    }
+
+    /**
+     * Set the milestone for this pull request.
+     */
+    public function setMilestone(int $milestoneNumber): static
+    {
+        $this->milestone()->set($milestoneNumber);
+
+        return $this;
+    }
+
     public function __get(string $name): mixed
     {
         return $this->data->{$name}; // @phpstan-ignore-line Variable property access is intentional for magic getter
diff --git a/src/Requests/CreateMilestone.php b/src/Requests/CreateMilestone.php
new file mode 100644
index 0000000..80c41cc
--- /dev/null
+++ b/src/Requests/CreateMilestone.php
@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Requests;
+
+use Saloon\Contracts\Body\HasBody;
+use Saloon\Enums\Method;
+use Saloon\Http\Request;
+use Saloon\Traits\Body\HasJsonBody;
+
+class CreateMilestone extends Request implements HasBody
+{
+    use HasJsonBody;
+
+    protected Method $method = Method::POST;
+
+    /**
+     * @param  array<string, mixed>  $data
+     */
+    public function __construct(
+        protected string $owner,
+        protected string $repo,
+        protected array $data,
+    ) {}
+
+    public function resolveEndpoint(): string
+    {
+        return "/repos/{$this->owner}/{$this->repo}/milestones";
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    protected function defaultBody(): array
+    {
+        return $this->data;
+    }
+}
diff --git a/src/Requests/DeleteMilestone.php b/src/Requests/DeleteMilestone.php
new file mode 100644
index 0000000..6eb6a0e
--- /dev/null
+++ b/src/Requests/DeleteMilestone.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Requests;
+
+use Saloon\Enums\Method;
+use Saloon\Http\Request;
+
+class DeleteMilestone extends Request
+{
+    protected Method $method = Method::DELETE;
+
+    public function __construct(
+        protected string $owner,
+        protected string $repo,
+        protected int $number,
+    ) {}
+
+    public function resolveEndpoint(): string
+    {
+        return "/repos/{$this->owner}/{$this->repo}/milestones/{$this->number}";
+    }
+}
diff --git a/src/Requests/GetMilestone.php b/src/Requests/GetMilestone.php
new file mode 100644
index 0000000..57a2f69
--- /dev/null
+++ b/src/Requests/GetMilestone.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Requests;
+
+use Saloon\Enums\Method;
+use Saloon\Http\Request;
+
+class GetMilestone extends Request
+{
+    protected Method $method = Method::GET;
+
+    public function __construct(
+        protected string $owner,
+        protected string $repo,
+        protected int $number,
+    ) {}
+
+    public function resolveEndpoint(): string
+    {
+        return "/repos/{$this->owner}/{$this->repo}/milestones/{$this->number}";
+    }
+}
diff --git a/src/Requests/ListMilestones.php b/src/Requests/ListMilestones.php
new file mode 100644
index 0000000..9d29e38
--- /dev/null
+++ b/src/Requests/ListMilestones.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Requests;
+
+use Saloon\Enums\Method;
+use Saloon\Http\Request;
+
+class ListMilestones extends Request
+{
+    protected Method $method = Method::GET;
+
+    public function __construct(
+        protected string $owner,
+        protected string $repo,
+        protected string $state = 'all',
+    ) {}
+
+    public function resolveEndpoint(): string
+    {
+        return "/repos/{$this->owner}/{$this->repo}/milestones";
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    protected function defaultQuery(): array
+    {
+        return ['state' => $this->state];
+    }
+}
diff --git a/src/Requests/UpdateMilestone.php b/src/Requests/UpdateMilestone.php
new file mode 100644
index 0000000..e6b643b
--- /dev/null
+++ b/src/Requests/UpdateMilestone.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Requests;
+
+use Saloon\Contracts\Body\HasBody;
+use Saloon\Enums\Method;
+use Saloon\Http\Request;
+use Saloon\Traits\Body\HasJsonBody;
+
+class UpdateMilestone extends Request implements HasBody
+{
+    use HasJsonBody;
+
+    protected Method $method = Method::PATCH;
+
+    /**
+     * @param  array<string, mixed>  $data
+     */
+    public function __construct(
+        protected string $owner,
+        protected string $repo,
+        protected int $number,
+        protected array $data,
+    ) {}
+
+    public function resolveEndpoint(): string
+    {
+        return "/repos/{$this->owner}/{$this->repo}/milestones/{$this->number}";
+    }
+
+    /**
+     * @return array<string, mixed>
+     */
+    protected function defaultBody(): array
+    {
+        return $this->data;
+    }
+}
diff --git a/src/Services/AssigneeManager.php b/src/Services/AssigneeManager.php
new file mode 100644
index 0000000..a27c171
--- /dev/null
+++ b/src/Services/AssigneeManager.php
@@ -0,0 +1,112 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Services;
+
+use ConduitUi\GitHubConnector\Connector;
+use ConduitUI\Pr\Contracts\AssigneeManagerInterface;
+use ConduitUI\Pr\DataTransferObjects\User;
+use ConduitUI\Pr\Requests\AddAssignees;
+use ConduitUI\Pr\Requests\GetPullRequest;
+use ConduitUI\Pr\Requests\RemoveAssignees;
+use Illuminate\Support\Collection;
+
+final class AssigneeManager implements AssigneeManagerInterface
+{
+    protected string $owner;
+
+    protected string $repo;
+
+    public function __construct(
+        protected Connector $connector,
+        string $fullName,
+        protected int $prNumber,
+    ) {
+        [$this->owner, $this->repo] = explode('/', $fullName, 2);
+    }
+
+    public function get(): Collection
+    {
+        $response = $this->connector->send(new GetPullRequest(
+            $this->owner,
+            $this->repo,
+            $this->prNumber
+        ));
+
+        /** @var array<string, mixed> $json */
+        $json = $response->json();
+
+        /** @var array<int, array<string, mixed>> $assignees */
+        $assignees = $json['assignees'] ?? [];
+
+        return collect($assignees)
+            ->map(fn (array $assignee): User => User::fromArray($assignee));
+    }
+
+    public function add(string $username): self
+    {
+        return $this->addMany([$username]);
+    }
+
+    public function addMany(array $usernames): self
+    {
+        $this->connector->send(new AddAssignees(
+            $this->owner,
+            $this->repo,
+            $this->prNumber,
+            $usernames
+        ));
+
+        return $this;
+    }
+
+    public function remove(string $username): self
+    {
+        return $this->removeMany([$username]);
+    }
+
+    public function removeMany(array $usernames): self
+    {
+        $this->connector->send(new RemoveAssignees(
+            $this->owner,
+            $this->repo,
+            $this->prNumber,
+            $usernames
+        ));
+
+        return $this;
+    }
+
+    public function replace(array $usernames): self
+    {
+        $current = $this->get()->pluck('login')->toArray();
+
+        if ($current !== []) {
+            $this->removeMany($current);
+        }
+
+        if ($usernames !== []) {
+            $this->addMany($usernames);
+        }
+
+        return $this;
+    }
+
+    public function clear(): self
+    {
+        $current = $this->get()->pluck('login')->toArray();
+
+        if ($current !== []) {
+            $this->removeMany($current);
+        }
+
+        return $this;
+    }
+
+    public function has(string $username): bool
+    {
+        return $this->get()
+            ->contains('login', $username);
+    }
+}
diff --git a/src/Services/MilestoneManager.php b/src/Services/MilestoneManager.php
new file mode 100644
index 0000000..2646229
--- /dev/null
+++ b/src/Services/MilestoneManager.php
@@ -0,0 +1,72 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Services;
+
+use ConduitUi\GitHubConnector\Connector;
+use ConduitUI\Pr\DataTransferObjects\Milestone;
+use ConduitUI\Pr\Requests\GetPullRequest;
+use ConduitUI\Pr\Requests\UpdatePullRequest;
+
+final class MilestoneManager
+{
+    protected string $owner;
+
+    protected string $repo;
+
+    public function __construct(
+        protected Connector $connector,
+        string $fullName,
+        protected int $prNumber,
+    ) {
+        [$this->owner, $this->repo] = explode('/', $fullName, 2);
+    }
+
+    public function get(): ?Milestone
+    {
+        $response = $this->connector->send(new GetPullRequest(
+            $this->owner,
+            $this->repo,
+            $this->prNumber
+        ));
+
+        /** @var array<string, mixed> $json */
+        $json = $response->json();
+
+        /** @var array<string, mixed>|null $milestone */
+        $milestone = $json['milestone'] ?? null;
+
+        return $milestone !== null ? Milestone::fromArray($milestone) : null;
+    }
+
+    public function set(int $milestoneNumber): Milestone
+    {
+        $response = $this->connector->send(new UpdatePullRequest(
+            $this->owner,
+            $this->repo,
+            $this->prNumber,
+            ['milestone' => $milestoneNumber]
+        ));
+
+        /** @var array<string, mixed> $json */
+        $json = $response->json();
+
+        /** @var array<string, mixed> $milestone */
+        $milestone = $json['milestone'];
+
+        return Milestone::fromArray($milestone);
+    }
+
+    public function remove(): bool
+    {
+        $response = $this->connector->send(new UpdatePullRequest(
+            $this->owner,
+            $this->repo,
+            $this->prNumber,
+            ['milestone' => null]
+        ));
+
+        return $response->successful();
+    }
+}
diff --git a/src/Services/RepositoryMilestoneManager.php b/src/Services/RepositoryMilestoneManager.php
new file mode 100644
index 0000000..f10ddbe
--- /dev/null
+++ b/src/Services/RepositoryMilestoneManager.php
@@ -0,0 +1,166 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ConduitUI\Pr\Services;
+
+use Carbon\Carbon;
+use ConduitUi\GitHubConnector\Connector;
+use ConduitUI\Pr\DataTransferObjects\Milestone;
+use ConduitUI\Pr\Requests\CreateMilestone;
+use ConduitUI\Pr\Requests\DeleteMilestone;
+use ConduitUI\Pr\Requests\GetMilestone;
+use ConduitUI\Pr\Requests\ListMilestones;
+use ConduitUI\Pr\Requests\UpdateMilestone;
+use Illuminate\Support\Collection;
+
+final class RepositoryMilestoneManager
+{
+    protected string $owner;
+
+    protected string $repo;
+
+    public function __construct(
+        protected Connector $connector,
+        string $fullName,
+    ) {
+        [$this->owner, $this->repo] = explode('/', $fullName, 2);
+    }
+
+    /**
+     * @return Collection<int, Milestone>
+     */
+    public function get(): Collection
+    {
+        $response = $this->connector->send(new ListMilestones(
+            $this->owner,
+            $this->repo,
+            'all'
+        ));
+
+        /** @var array<int, array<string, mixed>> $milestones */
+        $milestones = $response->json();
+
+        return collect($milestones)
+            ->map(fn (array $milestone): Milestone => Milestone::fromArray($milestone));
+    }
+
+    /**
+     * @return Collection<int, Milestone>
+     */
+    public function whereOpen(): Collection
+    {
+        $response = $this->connector->send(new ListMilestones(
+            $this->owner,
+            $this->repo,
+            'open'
+        ));
+
+        /** @var array<int, array<string, mixed>> $milestones */
+        $milestones = $response->json();
+
+        return collect($milestones)
+            ->map(fn (array $milestone): Milestone => Milestone::fromArray($milestone));
+    }
+
+    /**
+     * @return Collection<int, Milestone>
+     */
+    public function whereClosed(): Collection
+    {
+        $response = $this->connector->send(new ListMilestones(
+            $this->owner,
+            $this->repo,
+            'closed'
+        ));
+
+        /** @var array<int, array<string, mixed>> $milestones */
+        $milestones = $response->json();
+
+        return collect($milestones)
+            ->map(fn (array $milestone): Milestone => Milestone::fromArray($milestone));
+    }
+
+    public function find(int $number): Milestone
+    {
+        $response = $this->connector->send(new GetMilestone(
+            $this->owner,
+            $this->repo,
+            $number
+        ));
+
+        /** @var array<string, mixed> $milestone */
+        $milestone = $response->json();
+
+        return Milestone::fromArray($milestone);
+    }
+
+    public function create(
+        string $title,
+        ?string $description = null,
+        ?Carbon $dueOn = null,
+        string $state = 'open'
+    ): Milestone {
+        $data = [
+            'title' => $title,
+            'state' => $state,
+        ];
+
+        if ($description !== null) {
+            $data['description'] = $description;
+        }
+
+        if ($dueOn !== null) {
+            $data['due_on'] = $dueOn->toIso8601String();
+        }
+
+        $response = $this->connector->send(new CreateMilestone(
+            $this->owner,
+            $this->repo,
+            $data
+        ));
+
+        /** @var array<string, mixed> $milestone */
+        $milestone = $response->json();
+
+        return Milestone::fromArray($milestone);
+    }
+
+    public function update(
+        int $number,
+        ?string $title = null,
+        ?string $description = null,
+        ?Carbon $dueOn = null,
+        ?string $state = null
+    ): Milestone {
+        $data = array_filter([
+            'title' => $title,
+            'description' => $description,
+            'due_on' => $dueOn?->toIso8601String(),
+            'state' => $state,
+        ], fn ($value): bool => $value !== null);
+
+        $response = $this->connector->send(new UpdateMilestone(
+            $this->owner,
+            $this->repo,
+            $number,
+            $data
+        ));
+
+        /** @var array<string, mixed> $milestone */
+        $milestone = $response->json();
+
+        return Milestone::fromArray($milestone);
+    }
+
+    public function delete(int $number): bool
+    {
+        $response = $this->connector->send(new DeleteMilestone(
+            $this->owner,
+            $this->repo,
+            $number
+        ));
+
+        return $response->successful();
+    }
+}
diff --git a/tests/Unit/DataTransferObjects/MilestoneTest.php b/tests/Unit/DataTransferObjects/MilestoneTest.php
new file mode 100644
index 0000000..af085f6
--- /dev/null
+++ b/tests/Unit/DataTransferObjects/MilestoneTest.php
@@ -0,0 +1,232 @@
+<?php
+
+declare(strict_types=1);
+
+use Carbon\Carbon;
+use ConduitUI\Pr\DataTransferObjects\Milestone;
+
+beforeEach(function () {
+    Carbon::setTestNow('2025-01-15 12:00:00');
+});
+
+afterEach(function () {
+    Carbon::setTestNow();
+});
+
+it('can create milestone from array', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => 'First release',
+        'state' => 'open',
+        'open_issues' => 5,
+        'closed_issues' => 10,
+        'due_on' => '2025-12-31T23:59:59Z',
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    expect($milestone->number)->toBe(1)
+        ->and($milestone->title)->toBe('v1.0')
+        ->and($milestone->description)->toBe('First release')
+        ->and($milestone->state)->toBe('open')
+        ->and($milestone->openIssues)->toBe(5)
+        ->and($milestone->closedIssues)->toBe(10)
+        ->and($milestone->dueOn)->toBeInstanceOf(Carbon::class)
+        ->and($milestone->createdAt)->toBeInstanceOf(Carbon::class)
+        ->and($milestone->updatedAt)->toBeInstanceOf(Carbon::class)
+        ->and($milestone->closedAt)->toBeNull()
+        ->and($milestone->htmlUrl)->toBe('https://github.com/test/repo/milestone/1');
+});
+
+it('can create milestone from array with null description and due date', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 2,
+        'title' => 'v2.0',
+        'description' => null,
+        'state' => 'closed',
+        'open_issues' => 0,
+        'closed_issues' => 15,
+        'due_on' => null,
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => '2025-01-15T00:00:00Z',
+        'html_url' => 'https://github.com/test/repo/milestone/2',
+    ]);
+
+    expect($milestone->description)->toBeNull()
+        ->and($milestone->dueOn)->toBeNull()
+        ->and($milestone->closedAt)->toBeInstanceOf(Carbon::class);
+});
+
+it('can convert milestone to array', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => 'First release',
+        'state' => 'open',
+        'open_issues' => 5,
+        'closed_issues' => 10,
+        'due_on' => '2025-12-31T23:59:59Z',
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    $array = $milestone->toArray();
+
+    expect($array)->toBeArray()
+        ->and($array['number'])->toBe(1)
+        ->and($array['title'])->toBe('v1.0')
+        ->and($array['description'])->toBe('First release')
+        ->and($array['state'])->toBe('open');
+});
+
+it('correctly identifies open milestone', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => null,
+        'state' => 'open',
+        'open_issues' => 5,
+        'closed_issues' => 10,
+        'due_on' => null,
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    expect($milestone->isOpen())->toBeTrue()
+        ->and($milestone->isClosed())->toBeFalse();
+});
+
+it('correctly identifies closed milestone', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => null,
+        'state' => 'closed',
+        'open_issues' => 0,
+        'closed_issues' => 15,
+        'due_on' => null,
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => '2025-01-15T00:00:00Z',
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    expect($milestone->isClosed())->toBeTrue()
+        ->and($milestone->isOpen())->toBeFalse();
+});
+
+it('correctly identifies overdue milestone', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => null,
+        'state' => 'open',
+        'open_issues' => 5,
+        'closed_issues' => 10,
+        'due_on' => '2025-01-01T00:00:00Z', // Past date
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    expect($milestone->isOverdue())->toBeTrue();
+});
+
+it('identifies non-overdue milestone', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => null,
+        'state' => 'open',
+        'open_issues' => 5,
+        'closed_issues' => 10,
+        'due_on' => '2025-12-31T23:59:59Z', // Future date
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    expect($milestone->isOverdue())->toBeFalse();
+});
+
+it('identifies closed milestone as not overdue', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => null,
+        'state' => 'closed',
+        'open_issues' => 0,
+        'closed_issues' => 15,
+        'due_on' => '2025-01-01T00:00:00Z', // Past date but closed
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => '2025-01-14T00:00:00Z',
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    expect($milestone->isOverdue())->toBeFalse();
+});
+
+it('calculates progress correctly', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => null,
+        'state' => 'open',
+        'open_issues' => 5,
+        'closed_issues' => 10,
+        'due_on' => null,
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    expect($milestone->progress())->toBe(66.67);
+});
+
+it('returns zero progress when no issues exist', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => null,
+        'state' => 'open',
+        'open_issues' => 0,
+        'closed_issues' => 0,
+        'due_on' => null,
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    expect($milestone->progress())->toBe(0.0);
+});
+
+it('returns 100 percent progress when all issues closed', function () {
+    $milestone = Milestone::fromArray([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => null,
+        'state' => 'open',
+        'open_issues' => 0,
+        'closed_issues' => 15,
+        'due_on' => null,
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    expect($milestone->progress())->toBe(100.0);
+});
diff --git a/tests/Unit/PullRequestAssigneesAndMilestonesTest.php b/tests/Unit/PullRequestAssigneesAndMilestonesTest.php
new file mode 100644
index 0000000..23a4760
--- /dev/null
+++ b/tests/Unit/PullRequestAssigneesAndMilestonesTest.php
@@ -0,0 +1,134 @@
+<?php
+
+declare(strict_types=1);
+
+use Carbon\Carbon;
+use ConduitUi\GitHubConnector\Connector;
+use ConduitUI\Pr\DataTransferObjects\Base;
+use ConduitUI\Pr\DataTransferObjects\Head;
+use ConduitUI\Pr\DataTransferObjects\PullRequest as PullRequestData;
+use ConduitUI\Pr\DataTransferObjects\Repository;
+use ConduitUI\Pr\DataTransferObjects\User;
+use ConduitUI\Pr\PullRequest;
+use ConduitUI\Pr\Requests\UpdatePullRequest;
+use ConduitUI\Pr\Services\AssigneeManager;
+use ConduitUI\Pr\Services\MilestoneManager;
+use Saloon\Http\Request;
+use Saloon\Http\Response;
+
+class MockPullRequestAssigneeResponse extends Response
+{
+    public function __construct(private array $data = [])
+    {
+        // Skip parent constructor
+    }
+
+    public function json(string|int|null $key = null, mixed $default = null): mixed
+    {
+        if ($key !== null) {
+            return $this->data[$key] ?? $default;
+        }
+
+        return $this->data;
+    }
+
+    public function successful(): bool
+    {
+        return true;
+    }
+}
+
+class PullRequestAssigneeTestConnector extends Connector
+{
+    public ?Request $lastRequest = null;
+
+    public function __construct(private ?array $milestone = null)
+    {
+        parent::__construct('test-token');
+    }
+
+    public function send(Request $request, ...$args): Response
+    {
+        $this->lastRequest = $request;
+
+        return new MockPullRequestAssigneeResponse([
+            'milestone' => $this->milestone,
+        ]);
+    }
+}
+
+beforeEach(function () {
+    $this->prData = new PullRequestData(
+        number: 123,
+        title: 'Test PR',
+        body: 'Test body',
+        state: 'open',
+        user: new User(1, 'testuser', 'https://example.com/avatar.jpg', 'https://github.com/testuser', 'User'),
+        htmlUrl: 'https://github.com/test/test-repo/pull/123',
+        createdAt: Carbon::parse('2025-01-01')->toDateTimeImmutable(),
+        updatedAt: Carbon::parse('2025-01-15')->toDateTimeImmutable(),
+        closedAt: null,
+        mergedAt: null,
+        mergeCommitSha: null,
+        draft: false,
+        additions: 10,
+        deletions: 5,
+        changedFiles: 2,
+        assignee: null,
+        assignees: [],
+        requestedReviewers: [],
+        labels: [],
+        head: new Head(
+            'feature',
+            'abc123',
+            new User(1, 'testuser', 'https://example.com/avatar.jpg', 'https://github.com/testuser', 'User'),
+            new Repository(1, 'test-repo', 'test/test-repo', 'https://github.com/test/test-repo', false)
+        ),
+        base: new Base(
+            'main',
+            'def456',
+            new User(1, 'testuser', 'https://example.com/avatar.jpg', 'https://github.com/testuser', 'User'),
+            new Repository(1, 'test-repo', 'test/test-repo', 'https://github.com/test/test-repo', false)
+        ),
+    );
+});
+
+it('returns assignee manager instance', function () {
+    $connector = new PullRequestAssigneeTestConnector;
+    $pr = new PullRequest($connector, 'test', 'repo', $this->prData);
+
+    $assignees = $pr->assignees();
+
+    expect($assignees)->toBeInstanceOf(AssigneeManager::class);
+});
+
+it('returns milestone manager instance', function () {
+    $connector = new PullRequestAssigneeTestConnector;
+    $pr = new PullRequest($connector, 'test', 'repo', $this->prData);
+
+    $milestone = $pr->milestone();
+
+    expect($milestone)->toBeInstanceOf(MilestoneManager::class);
+});
+
+it('can set milestone on pull request', function () {
+    $connector = new PullRequestAssigneeTestConnector([
+        'number' => 5,
+        'title' => 'v2.0',
+        'description' => 'Second release',
+        'state' => 'open',
+        'open_issues' => 3,
+        'closed_issues' => 7,
+        'due_on' => '2025-06-30T23:59:59Z',
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/5',
+    ]);
+
+    $pr = new PullRequest($connector, 'test', 'repo', $this->prData);
+    $result = $pr->setMilestone(5);
+
+    expect($result)->toBeInstanceOf(PullRequest::class)
+        ->and($connector->lastRequest)->toBeInstanceOf(UpdatePullRequest::class);
+});
diff --git a/tests/Unit/Requests/MilestoneRequestsTest.php b/tests/Unit/Requests/MilestoneRequestsTest.php
new file mode 100644
index 0000000..307f76a
--- /dev/null
+++ b/tests/Unit/Requests/MilestoneRequestsTest.php
@@ -0,0 +1,86 @@
+<?php
+
+declare(strict_types=1);
+
+use ConduitUI\Pr\Requests\CreateMilestone;
+use ConduitUI\Pr\Requests\DeleteMilestone;
+use ConduitUI\Pr\Requests\GetMilestone;
+use ConduitUI\Pr\Requests\ListMilestones;
+use ConduitUI\Pr\Requests\UpdateMilestone;
+
+it('GetMilestone has correct endpoint', function () {
+    $request = new GetMilestone('owner', 'repo', 5);
+
+    expect($request->resolveEndpoint())->toBe('/repos/owner/repo/milestones/5');
+});
+
+it('ListMilestones has correct endpoint', function () {
+    $request = new ListMilestones('owner', 'repo', 'all');
+
+    expect($request->resolveEndpoint())->toBe('/repos/owner/repo/milestones');
+});
+
+it('ListMilestones has correct query parameters for open state', function () {
+    $request = new ListMilestones('owner', 'repo', 'open');
+    $reflection = new ReflectionClass($request);
+    $method = $reflection->getMethod('defaultQuery');
+
+    $query = $method->invoke($request);
+
+    expect($query)->toBe(['state' => 'open']);
+});
+
+it('ListMilestones has correct query parameters for closed state', function () {
+    $request = new ListMilestones('owner', 'repo', 'closed');
+    $reflection = new ReflectionClass($request);
+    $method = $reflection->getMethod('defaultQuery');
+
+    $query = $method->invoke($request);
+
+    expect($query)->toBe(['state' => 'closed']);
+});
+
+it('CreateMilestone has correct endpoint', function () {
+    $request = new CreateMilestone('owner', 'repo', ['title' => 'v1.0']);
+
+    expect($request->resolveEndpoint())->toBe('/repos/owner/repo/milestones');
+});
+
+it('CreateMilestone has correct body', function () {
+    $data = [
+        'title' => 'v1.0',
+        'description' => 'First release',
+        'due_on' => '2025-12-31T23:59:59Z',
+        'state' => 'open',
+    ];
+    $request = new CreateMilestone('owner', 'repo', $data);
+    $reflection = new ReflectionClass($request);
+    $method = $reflection->getMethod('defaultBody');
+
+    $body = $method->invoke($request);
+
+    expect($body)->toBe($data);
+});
+
+it('UpdateMilestone has correct endpoint', function () {
+    $request = new UpdateMilestone('owner', 'repo', 5, ['title' => 'v1.0']);
+
+    expect($request->resolveEndpoint())->toBe('/repos/owner/repo/milestones/5');
+});
+
+it('UpdateMilestone has correct body', function () {
+    $data = ['title' => 'v1.0 Updated'];
+    $request = new UpdateMilestone('owner', 'repo', 5, $data);
+    $reflection = new ReflectionClass($request);
+    $method = $reflection->getMethod('defaultBody');
+
+    $body = $method->invoke($request);
+
+    expect($body)->toBe($data);
+});
+
+it('DeleteMilestone has correct endpoint', function () {
+    $request = new DeleteMilestone('owner', 'repo', 5);
+
+    expect($request->resolveEndpoint())->toBe('/repos/owner/repo/milestones/5');
+});
diff --git a/tests/Unit/Services/AssigneeManagerTest.php b/tests/Unit/Services/AssigneeManagerTest.php
new file mode 100644
index 0000000..6b56e22
--- /dev/null
+++ b/tests/Unit/Services/AssigneeManagerTest.php
@@ -0,0 +1,161 @@
+<?php
+
+declare(strict_types=1);
+
+use ConduitUi\GitHubConnector\Connector;
+use ConduitUI\Pr\DataTransferObjects\User;
+use ConduitUI\Pr\Requests\AddAssignees;
+use ConduitUI\Pr\Requests\RemoveAssignees;
+use ConduitUI\Pr\Services\AssigneeManager;
+use Saloon\Http\Request;
+use Saloon\Http\Response;
+
+class MockAssigneeManagerResponse extends Response
+{
+    public function __construct(private array $data = [])
+    {
+        // Skip parent constructor
+    }
+
+    public function json(string|int|null $key = null, mixed $default = null): mixed
+    {
+        if ($key !== null) {
+            return $this->data[$key] ?? $default;
+        }
+
+        return $this->data;
+    }
+
+    public function successful(): bool
+    {
+        return true;
+    }
+}
+
+class AssigneeManagerTestConnector extends Connector
+{
+    public ?Request $lastRequest = null;
+
+    public function __construct(private array $assignees = [])
+    {
+        parent::__construct('test-token');
+    }
+
+    public function send(Request $request, ...$args): Response
+    {
+        $this->lastRequest = $request;
+
+        return new MockAssigneeManagerResponse([
+            'assignees' => $this->assignees,
+        ]);
+    }
+}
+
+it('can get assignees', function () {
+    $connector = new AssigneeManagerTestConnector([
+        ['id' => 1, 'login' => 'user1', 'avatar_url' => 'https://example.com/1.jpg', 'html_url' => 'https://github.com/user1', 'type' => 'User'],
+        ['id' => 2, 'login' => 'user2', 'avatar_url' => 'https://example.com/2.jpg', 'html_url' => 'https://github.com/user2', 'type' => 'User'],
+    ]);
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+    $assignees = $manager->get();
+
+    expect($assignees)->toHaveCount(2)
+        ->and($assignees->first())->toBeInstanceOf(User::class)
+        ->and($assignees->first()->login)->toBe('user1')
+        ->and($assignees->last()->login)->toBe('user2');
+});
+
+it('can add single assignee', function () {
+    $connector = new AssigneeManagerTestConnector;
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+    $result = $manager->add('newuser');
+
+    expect($result)->toBeInstanceOf(AssigneeManager::class)
+        ->and($connector->lastRequest)->toBeInstanceOf(AddAssignees::class);
+});
+
+it('can add multiple assignees', function () {
+    $connector = new AssigneeManagerTestConnector;
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+    $result = $manager->addMany(['user1', 'user2', 'user3']);
+
+    expect($result)->toBeInstanceOf(AssigneeManager::class)
+        ->and($connector->lastRequest)->toBeInstanceOf(AddAssignees::class);
+});
+
+it('can remove single assignee', function () {
+    $connector = new AssigneeManagerTestConnector;
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+    $result = $manager->remove('user1');
+
+    expect($result)->toBeInstanceOf(AssigneeManager::class)
+        ->and($connector->lastRequest)->toBeInstanceOf(RemoveAssignees::class);
+});
+
+it('can remove multiple assignees', function () {
+    $connector = new AssigneeManagerTestConnector;
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+    $result = $manager->removeMany(['user1', 'user2']);
+
+    expect($result)->toBeInstanceOf(AssigneeManager::class)
+        ->and($connector->lastRequest)->toBeInstanceOf(RemoveAssignees::class);
+});
+
+it('can replace assignees', function () {
+    $connector = new AssigneeManagerTestConnector([
+        ['id' => 1, 'login' => 'olduser', 'avatar_url' => 'https://example.com/1.jpg', 'html_url' => 'https://github.com/olduser', 'type' => 'User'],
+    ]);
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+    $result = $manager->replace(['newuser1', 'newuser2']);
+
+    expect($result)->toBeInstanceOf(AssigneeManager::class);
+});
+
+it('can replace empty assignees', function () {
+    $connector = new AssigneeManagerTestConnector;
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+    $result = $manager->replace(['newuser1', 'newuser2']);
+
+    expect($result)->toBeInstanceOf(AssigneeManager::class)
+        ->and($connector->lastRequest)->toBeInstanceOf(AddAssignees::class);
+});
+
+it('can clear assignees', function () {
+    $connector = new AssigneeManagerTestConnector([
+        ['id' => 1, 'login' => 'user1', 'avatar_url' => 'https://example.com/1.jpg', 'html_url' => 'https://github.com/user1', 'type' => 'User'],
+    ]);
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+    $result = $manager->clear();
+
+    expect($result)->toBeInstanceOf(AssigneeManager::class);
+});
+
+it('clear does nothing when no assignees exist', function () {
+    $connector = new AssigneeManagerTestConnector([]);
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+    $result = $manager->clear();
+
+    expect($result)->toBeInstanceOf(AssigneeManager::class);
+});
+
+it('can check if user is assigned', function () {
+    $connector = new AssigneeManagerTestConnector([
+        ['id' => 1, 'login' => 'user1', 'avatar_url' => 'https://example.com/1.jpg', 'html_url' => 'https://github.com/user1', 'type' => 'User'],
+        ['id' => 2, 'login' => 'user2', 'avatar_url' => 'https://example.com/2.jpg', 'html_url' => 'https://github.com/user2', 'type' => 'User'],
+    ]);
+
+    $manager = new AssigneeManager($connector, 'test/repo', 123);
+
+    expect($manager->has('user1'))->toBeTrue()
+        ->and($manager->has('user2'))->toBeTrue()
+        ->and($manager->has('user3'))->toBeFalse();
+});
diff --git a/tests/Unit/Services/MilestoneManagerTest.php b/tests/Unit/Services/MilestoneManagerTest.php
new file mode 100644
index 0000000..70fcc97
--- /dev/null
+++ b/tests/Unit/Services/MilestoneManagerTest.php
@@ -0,0 +1,116 @@
+<?php
+
+declare(strict_types=1);
+
+use ConduitUi\GitHubConnector\Connector;
+use ConduitUI\Pr\DataTransferObjects\Milestone;
+use ConduitUI\Pr\Requests\UpdatePullRequest;
+use ConduitUI\Pr\Services\MilestoneManager;
+use Saloon\Http\Request;
+use Saloon\Http\Response;
+
+class MockMilestoneManagerResponse extends Response
+{
+    public function __construct(private array $data = [])
+    {
+        // Skip parent constructor
+    }
+
+    public function json(string|int|null $key = null, mixed $default = null): mixed
+    {
+        if ($key !== null) {
+            return $this->data[$key] ?? $default;
+        }
+
+        return $this->data;
+    }
+
+    public function successful(): bool
+    {
+        return true;
+    }
+}
+
+class MilestoneManagerTestConnector extends Connector
+{
+    public ?Request $lastRequest = null;
+
+    public function __construct(private ?array $milestone = null)
+    {
+        parent::__construct('test-token');
+    }
+
+    public function send(Request $request, ...$args): Response
+    {
+        $this->lastRequest = $request;
+
+        return new MockMilestoneManagerResponse([
+            'milestone' => $this->milestone,
+        ]);
+    }
+}
+
+it('can get milestone', function () {
+    $connector = new MilestoneManagerTestConnector([
+        'number' => 1,
+        'title' => 'v1.0',
+        'description' => 'First release',
+        'state' => 'open',
+        'open_issues' => 5,
+        'closed_issues' => 10,
+        'due_on' => '2025-12-31T23:59:59Z',
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/1',
+    ]);
+
+    $manager = new MilestoneManager($connector, 'test/repo', 123);
+    $milestone = $manager->get();
+
+    expect($milestone)->toBeInstanceOf(Milestone::class)
+        ->and($milestone->number)->toBe(1)
+        ->and($milestone->title)->toBe('v1.0');
+});
+
+it('returns null when no milestone exists', function () {
+    $connector = new MilestoneManagerTestConnector(null);
+
+    $manager = new MilestoneManager($connector, 'test/repo', 123);
+    $milestone = $manager->get();
+
+    expect($milestone)->toBeNull();
+});
+
+it('can set milestone', function () {
+    $connector = new MilestoneManagerTestConnector([
+        'number' => 5,
+        'title' => 'v2.0',
+        'description' => 'Second release',
+        'state' => 'open',
+        'open_issues' => 3,
+        'closed_issues' => 7,
+        'due_on' => '2025-06-30T23:59:59Z',
+        'created_at' => '2025-01-01T00:00:00Z',
+        'updated_at' => '2025-01-15T00:00:00Z',
+        'closed_at' => null,
+        'html_url' => 'https://github.com/test/repo/milestone/5',
+    ]);
+
+    $manager = new MilestoneManager($connector, 'test/repo', 123);
+    $milestone = $manager->set(5);
+
+    expect($milestone)->toBeInstanceOf(Milestone::class)
+        ->and($milestone->number)->toBe(5)
+        ->and($connector->lastRequest)->toBeInstanceOf(UpdatePullRequest::class);
+});
+
+it('can remove milestone', function () {
+    $connector = new MilestoneManagerTestConnector(null);
+
+    $manager = new MilestoneManager($connector, 'test/repo', 123);
+    $result = $manager->remove();
+
+    expect($result)->toBeTrue()
+        ->and($connector->lastRequest)->toBeInstanceOf(UpdatePullRequest::class);
+});
diff --git a/tests/Unit/Services/RepositoryMilestoneManagerTest.php b/tests/Unit/Services/RepositoryMilestoneManagerTest.php
new file mode 100644
index 0000000..55c3aad
--- /dev/null
+++ b/tests/Unit/Services/RepositoryMilestoneManagerTest.php
@@ -0,0 +1,306 @@
+<?php
+
+declare(strict_types=1);
+
+use Carbon\Carbon;
+use ConduitUi\GitHubConnector\Connector;
+use ConduitUI\Pr\DataTransferObjects\Milestone;
+use ConduitUI\Pr\Requests\CreateMilestone;
+use ConduitUI\Pr\Requests\DeleteMilestone;
+use ConduitUI\Pr\Requests\GetMilestone;
+use ConduitUI\Pr\Requests\ListMilestones;
+use ConduitUI\Pr\Requests\UpdateMilestone;
+use ConduitUI\Pr\Services\RepositoryMilestoneManager;
+use Saloon\Http\Request;
+use Saloon\Http\Response;
+
+class MockRepositoryMilestoneManagerResponse extends Response
+{
+    public function __construct(private array|bool $data = [])
+    {
+        // Skip parent constructor
+    }
+
+    public function json(string|int|null $key = null, mixed $default = null): mixed
+    {
+        if ($key !== null) {
+            return $this->data[$key] ?? $default;
+        }
+
+        return $this->data;
+    }
+
+    public function successful(): bool
+    {
+        return $this->data !== false;
+    }
+}
+
+class RepositoryMilestoneManagerTestConnector extends Connector
+{
+    public ?Request $lastRequest = null;
+
+    public function __construct(
+        private array $milestones = [],
+        private ?array $singleMilestone = null,
+        private bool $operationSuccess = true
+    ) {
+        parent::__construct('test-token');
+    }
+
+    public function send(Request $request, ...$args): Response
+    {
+        $this->lastRequest = $request;
+
+        if ($request instanceof ListMilestones) {
+            return new MockRepositoryMilestoneManagerResponse($this->milestones);
+        }
+
+        if ($request instanceof GetMilestone || $request instanceof CreateMilestone || $request instanceof UpdateMilestone) {
+            return new MockRepositoryMilestoneManagerResponse($this->singleMilestone ?? []);
+        }
+
+        if ($request instanceof DeleteMilestone) {
+            return new MockRepositoryMilestoneManagerResponse($this->operationSuccess);
+        }
+
+        return new MockRepositoryMilestoneManagerResponse([]);
+    }
+}
+
+it('can get all milestones', function () {
+    $connector = new RepositoryMilestoneManagerTestConnector([
+        [
+            'number' => 1,
+            'title' => 'v1.0',
+            'description' => 'First release',
+            'state' => 'open',
+            'open_issues' => 5,
+            'closed_issues' => 10,
+            'due_on' => '2025-12-31T23:59:59Z',
+            'created_at' => '2025-01-01T00:00:00Z',
+            'updated_at' => '2025-01-15T00:00:00Z',
+            'closed_at' => null,
+            'html_url' => 'https://github.com/test/repo/milestone/1',
+        ],
+        [
+            'number' => 2,
+            'title' => 'v2.0',
+            'description' => 'Second release',
+            'state' => 'closed',
+            'open_issues' => 0,
+            'closed_issues' => 15,
+            'due_on' => null,
+            'created_at' => '2025-01-01T00:00:00Z',
+            'updated_at' => '2025-01-15T00:00:00Z',
+            'closed_at' => '2025-01-14T00:00:00Z',
+            'html_url' => 'https://github.com/test/repo/milestone/2',
+        ],
+    ]);
+
+    $manager = new RepositoryMilestoneManager($connector, 'test/repo');
+    $milestones = $manager->get();
+
+    expect($milestones)->toHaveCount(2)
+        ->and($milestones->first())->toBeInstanceOf(Milestone::class)
+        ->and($milestones->first()->title)->toBe('v1.0')
+        ->and($milestones->last()->title)->toBe('v2.0');
+});
+
+it('can get open milestones', function () {
+    $connector = new RepositoryMilestoneManagerTestConnector([
+        [
+            'number' => 1,
+            'title' => 'v1.0',
+            'description' => 'First release',
+            'state' => 'open',
+            'open_issues' => 5,
+            'closed_issues' => 10,
+            'due_on' => '2025-12-31T23:59:59Z',
+            'created_at' => '2025-01-01T00:00:00Z',
+            'updated_at' => '2025-01-15T00:00:00Z',
+            'closed_at' => null,
+            'html_url' => 'https://github.com/test/repo/milestone/1',
+        ],
+    ]);
+
+    $manager = new RepositoryMilestoneManager($connector, 'test/repo');
+    $milestones = $manager->whereOpen();
+
+    expect($milestones)->toHaveCount(1)
+        ->and($milestones->first()->state)->toBe('open');
+});
+
+it('can get closed milestones', function () {
+    $connector = new RepositoryMilestoneManagerTestConnector([
+        [
+            'number' => 2,
+            'title' => 'v2.0',
+            'description' => 'Second release',
+            'state' => 'closed',
+            'open_issues' => 0,
+            'closed_issues' => 15,
+            'due_on' => null,
+            'created_at' => '2025-01-01T00:00:00Z',
+            'updated_at' => '2025-01-15T00:00:00Z',
+            'closed_at' => '2025-01-14T00:00:00Z',
+            'html_url' => 'https://github.com/test/repo/milestone/2',
+        ],
+    ]);
+
+    $manager = new RepositoryMilestoneManager($connector, 'test/repo');
+    $milestones = $manager->whereClosed();
+
+    expect($milestones)->toHaveCount(1)
+        ->and($milestones->first()->state)->toBe('closed');
+});
+
+it('can find specific milestone', function () {
+    $connector = new RepositoryMilestoneManagerTestConnector(
+        [],
+        [
+            'number' => 1,
+            'title' => 'v1.0',
+            'description' => 'First release',
+            'state' => 'open',
+            'open_issues' => 5,
+            'closed_issues' => 10,
+            'due_on' => '2025-12-31T23:59:59Z',
+            'created_at' => '2025-01-01T00:00:00Z',
+            'updated_at' => '2025-01-15T00:00:00Z',
+            'closed_at' => null,
+            'html_url' => 'https://github.com/test/repo/milestone/1',
+        ]
+    );
+
+    $manager = new RepositoryMilestoneManager($connector, 'test/repo');
+    $milestone = $manager->find(1);
+
+    expect($milestone)->toBeInstanceOf(Milestone::class)
+        ->and($milestone->number)->toBe(1)
+        ->and($connector->lastRequest)->toBeInstanceOf(GetMilestone::class);
+});
+
+it('can create milestone with all parameters', function () {
+    $connector = new RepositoryMilestoneManagerTestConnector(
+        [],
+        [
+            'number' => 3,
+            'title' => 'v3.0',
+            'description' => 'Third release',
+            'state' => 'open',
+            'open_issues' => 0,
+            'closed_issues' => 0,
+            'due_on' => '2025-12-31T23:59:59Z',
+            'created_at' => '2025-01-15T00:00:00Z',
+            'updated_at' => '2025-01-15T00:00:00Z',
+            'closed_at' => null,
+            'html_url' => 'https://github.com/test/repo/milestone/3',
+        ]
+    );
+
+    $manager = new RepositoryMilestoneManager($connector, 'test/repo');
+    $milestone = $manager->create(
+        'v3.0',
+        'Third release',
+        Carbon::parse('2025-12-31T23:59:59Z'),
+        'open'
+    );
+
+    expect($milestone)->toBeInstanceOf(Milestone::class)
+        ->and($milestone->title)->toBe('v3.0')
+        ->and($connector->lastRequest)->toBeInstanceOf(CreateMilestone::class);
+});
+
+it('can create milestone with minimal parameters', function () {
+    $connector = new RepositoryMilestoneManagerTestConnector(
+        [],
+        [
+            'number' => 4,
+            'title' => 'v4.0',
+            'description' => null,
+            'state' => 'open',
+            'open_issues' => 0,
+            'closed_issues' => 0,
+            'due_on' => null,
+            'created_at' => '2025-01-15T00:00:00Z',
+            'updated_at' => '2025-01-15T00:00:00Z',
+            'closed_at' => null,
+            'html_url' => 'https://github.com/test/repo/milestone/4',
+        ]
+    );
+
+    $manager = new RepositoryMilestoneManager($connector, 'test/repo');
+    $milestone = $manager->create('v4.0');
+
+    expect($milestone)->toBeInstanceOf(Milestone::class)
+        ->and($milestone->title)->toBe('v4.0')
+        ->and($milestone->description)->toBeNull();
+});
+
+it('can update milestone', function () {
+    $connector = new RepositoryMilestoneManagerTestConnector(
+        [],
+        [
+            'number' => 1,
+            'title' => 'v1.0 Updated',
+            'description' => 'Updated description',
+            'state' => 'closed',
+            'open_issues' => 0,
+            'closed_issues' => 15,
+            'due_on' => '2025-12-31T23:59:59Z',
+            'created_at' => '2025-01-01T00:00:00Z',
+            'updated_at' => '2025-01-15T12:00:00Z',
+            'closed_at' => '2025-01-15T12:00:00Z',
+            'html_url' => 'https://github.com/test/repo/milestone/1',
+        ]
+    );
+
+    $manager = new RepositoryMilestoneManager($connector, 'test/repo');
+    $milestone = $manager->update(
+        1,
+        'v1.0 Updated',
+        'Updated description',
+        Carbon::parse('2025-12-31T23:59:59Z'),
+        'closed'
+    );
+
+    expect($milestone)->toBeInstanceOf(Milestone::class)
+        ->and($milestone->title)->toBe('v1.0 Updated')
+        ->and($connector->lastRequest)->toBeInstanceOf(UpdateMilestone::class);
+});
+
+it('can update milestone with partial parameters', function () {
+    $connector = new RepositoryMilestoneManagerTestConnector(
+        [],
+        [
+            'number' => 1,
+            'title' => 'v1.0',
+            'description' => 'First release',
+            'state' => 'closed',
+            'open_issues' => 0,
+            'closed_issues' => 15,
+            'due_on' => '2025-12-31T23:59:59Z',
+            'created_at' => '2025-01-01T00:00:00Z',
+            'updated_at' => '2025-01-15T12:00:00Z',
+            'closed_at' => '2025-01-15T12:00:00Z',
+            'html_url' => 'https://github.com/test/repo/milestone/1',
+        ]
+    );
+
+    $manager = new RepositoryMilestoneManager($connector, 'test/repo');
+    $milestone = $manager->update(1, null, null, null, 'closed');
+
+    expect($milestone)->toBeInstanceOf(Milestone::class)
+        ->and($milestone->state)->toBe('closed');
+});
+
+it('can delete milestone', function () {
+    $connector = new RepositoryMilestoneManagerTestConnector([], null, true);
+
+    $manager = new RepositoryMilestoneManager($connector, 'test/repo');
+    $result = $manager->delete(1);
+
+    expect($result)->toBeTrue()
+        ->and($connector->lastRequest)->toBeInstanceOf(DeleteMilestone::class);
+});