此问题可能是由于相同的文件名引起的，因此可以通过使用FactoryBot的序列来确保每个文件有唯一的名称来解决。以下是示例代码：

# 在factory文件中定义序列
FactoryBot.define do
  factory :file_attachment, class: 'ActiveStorage::Attachment' do
    record { nil }
    blob { nil }
  
    sequence(:name) { |n| "file_#{n}.jpg" }
  
    after(:build) do |attachment, evaluator|
      blob = evaluator.blob || create(:file_blob)
      attachment.name ||= blob.filename
      attachment.record ||= create(:post)
      attachment.blob ||= blob
    end
  end
end

# 在测试中使用序列
describe Post do
  let(:file_attachment) { build(:file_attachment) }
  
  it 'creates a file attachment with a unique name' do
    expect(file_attachment.name).not_to be_nil
    expect(file_attachment.name).not_to eq build(:file_attachment).name
  end
end