```ruby
require_relative '../lib/statistics'

describe Workerholic::Statistics do
  it 'initializes attributes with without an argument' do
    statistics = Workerholic::Statistics.new
    expect(statistics.enqueued_at).to be_nil
    expect(statistics.retry_count).to eq(0)
    expect(statistics.errors).to eq([])
    expect(statistics.started_at).to be_nil
    expect(statistics.completed_at).to be_nil
  end
end
```

Add spec for to_hash method
user
```ruby
require_relative '../lib/statistics'

describe Workerholic::Statistics do
  it 'initializes attributes with without an argument' do
    statistics = Workerholic::Statistics.new
    expect(statistics.enqueued_at).to be_nil
    expect(statistics.retry_count).to eq(0)
    expect(statistics.errors).to eq([])
    expect(statistics.started_at).to be_nil
    expect(statistics.completed_at).to be_nil
  end

  it 'initializes attributes with arguments' do
    enqueuing_time = Time.now.to_f - 86400
    started_at_time = Time.now.to_f
    completed_at_time = Time.now.to_f + 86400
    options = {
      enqueued_at: enqueuing_time,
      retry_count: 4,
      errors: ['Your job is bad and you should feel bad'],
      started_at: started_at_time,
      completed_at: completed_at_time
    }

    expect(Workerholic::Statistics.new(options).to_hash).to eq(options)  
  end
end
```
assistant