test DeleteComment use case

backend/tests/Unit/Comment/UseCases/DeleteCommentTest.php

@@ -0,0 +1,131 @@
+<?php
+
+namespace Tests\Unit\Comment\UseCases;
+
+use App\Comment\Comment;
+use App\Comment\CreateCommentDto;
+use App\Comment\UseCases\DeleteComment\DeleteComment;
+use App\Comment\UseCases\DeleteComment\DeleteCommentRequest;
+use App\Exceptions\BadRequestException;
+use App\Exceptions\ForbiddenException;
+use DateTimeImmutable;
+use DateTimeZone;
+use Tests\Fakes\FakeCommentRepository;
+use Tests\TestCase;
+
+class DeleteCommentTest extends TestCase
+{
+    private FakeCommentRepository $commentRepo;
+
+    private DateTimeImmutable $now;
+
+    private DeleteComment $useCase;
+
+    protected function setUp(): void
+    {
+        $this->now = new DateTimeImmutable(
+            '2026-05-06T12:00:00',
+            new DateTimeZone('UTC'),
+        );
+        $this->commentRepo = new FakeCommentRepository;
+        $this->useCase = new DeleteComment($this->commentRepo);
+    }
+
+    private function seedCommentByUser(int $userId): Comment
+    {
+        return $this->commentRepo->create(new CreateCommentDto(
+            postId: 1,
+            userId: $userId,
+            body: 'comment body',
+            createdAt: $this->now,
+        ));
+    }
+
+    public function test_zero_comment_id_throws_bad_request(): void
+    {
+        $this->expectException(BadRequestException::class);
+        $this->useCase->execute(new DeleteCommentRequest(
+            commentId: 0,
+            requesterId: 1,
+            requesterIsAdmin: false,
+        ));
+    }
+
+    public function test_zero_requester_id_throws_bad_request(): void
+    {
+        $comment = $this->seedCommentByUser(1);
+
+        $this->expectException(BadRequestException::class);
+        $this->useCase->execute(new DeleteCommentRequest(
+            commentId: $comment->getId(),
+            requesterId: 0,
+            requesterIsAdmin: false,
+        ));
+    }
+
+    public function test_unknown_comment_is_no_op(): void
+    {
+        $this->useCase->execute(new DeleteCommentRequest(
+            commentId: 999,
+            requesterId: 1,
+            requesterIsAdmin: false,
+        ));
+
+        $this->assertNull($this->commentRepo->find(999));
+    }
+
+    public function test_author_can_delete_own_comment(): void
+    {
+        $comment = $this->seedCommentByUser(1);
+
+        $this->useCase->execute(new DeleteCommentRequest(
+            commentId: $comment->getId(),
+            requesterId: 1,
+            requesterIsAdmin: false,
+        ));
+
+        $this->assertNull($this->commentRepo->find($comment->getId()));
+    }
+
+    public function test_admin_can_delete_anyones_comment(): void
+    {
+        $comment = $this->seedCommentByUser(1);
+
+        $this->useCase->execute(new DeleteCommentRequest(
+            commentId: $comment->getId(),
+            requesterId: 99,
+            requesterIsAdmin: true,
+        ));
+
+        $this->assertNull($this->commentRepo->find($comment->getId()));
+    }
+
+    public function test_other_user_cannot_delete_comment(): void
+    {
+        $comment = $this->seedCommentByUser(1);
+
+        $this->expectException(ForbiddenException::class);
+        $this->useCase->execute(new DeleteCommentRequest(
+            commentId: $comment->getId(),
+            requesterId: 2,
+            requesterIsAdmin: false,
+        ));
+    }
+
+    public function test_forbidden_delete_does_not_remove_comment(): void
+    {
+        $comment = $this->seedCommentByUser(1);
+
+        try {
+            $this->useCase->execute(new DeleteCommentRequest(
+                commentId: $comment->getId(),
+                requesterId: 2,
+                requesterIsAdmin: false,
+            ));
+        } catch (ForbiddenException) {
+            // expected
+        }
+
+        $this->assertNotNull($this->commentRepo->find($comment->getId()));
+    }
+}