feat: stabilize social backend contracts

src/modules/follows/follows.service.spec.ts

@@ -21,12 +21,16 @@ describe('FollowsService', () => {
     const outboxService = {
       enqueueFollowNotification: jest.fn().mockRejectedValue(new Error('socket down')),
     };
+    const blocksRepository = {
+      findAnyBetween: jest.fn().mockResolvedValue(null),
+    };
 
     const service = new FollowsService(
       followsRepository as any,
       usersRepository as any,
       outboxService as any,
       { bumpGlobalVersion: jest.fn().mockResolvedValue(1) } as any,
+      blocksRepository as any,
     );
 
     await expect(service.toggleFollow(currentUserId, { targetUserId })).resolves.toEqual({
@@ -40,4 +44,51 @@ describe('FollowsService', () => {
       'follow-1',
     );
   });
+
+  it('prevents users from following themselves', async () => {
+    const userId = '507f1f77bcf86cd799439011';
+    const service = new FollowsService(
+      {} as any,
+      {} as any,
+      {} as any,
+      { bumpGlobalVersion: jest.fn() } as any,
+      { findAnyBetween: jest.fn() } as any,
+    );
+
+    await expect(service.followUser(userId, userId)).rejects.toThrow('You cannot follow yourself');
+  });
+
+  it('returns already-following response without creating duplicate notification', async () => {
+    const currentUserId = '507f1f77bcf86cd799439011';
+    const targetUserId = '507f191e810c19729de860ea';
+    const followsRepository = {
+      findOne: jest.fn().mockResolvedValue({ id: 'existing-follow' }),
+      count: jest.fn().mockResolvedValueOnce(1).mockResolvedValueOnce(2),
+      create: jest.fn(),
+    };
+    const usersRepository = {
+      findById: jest.fn().mockResolvedValue({ id: targetUserId, isDisabled: false, isPrivate: false }),
+      setFollowingCount: jest.fn(),
+      setFollowersCount: jest.fn(),
+    };
+    const outboxService = {
+      enqueueFollowNotification: jest.fn(),
+    };
+    const service = new FollowsService(
+      followsRepository as any,
+      usersRepository as any,
+      outboxService as any,
+      { bumpGlobalVersion: jest.fn() } as any,
+      { findAnyBetween: jest.fn().mockResolvedValue(null) } as any,
+    );
+
+    await expect(service.followUser(currentUserId, targetUserId)).resolves.toMatchObject({
+      message: 'Already following user',
+      isFollowing: true,
+      followersCount: 2,
+      followingCount: 1,
+    });
+    expect(followsRepository.create).not.toHaveBeenCalled();
+    expect(outboxService.enqueueFollowNotification).not.toHaveBeenCalled();
+  });
 });