```ruby
# encoding: utf-8

require 'spec_helper'

describe 'null integration' do

  let(:base_cmd) { 'bundle exec mutant -I lib --require test_app "::TestApp*"' }

  around do |example|
    Dir.chdir(TestApp.root) do
      example.run
    end
  end

  specify 'it allows to kill mutations' do
    expect(Kernel.system(base_cmd)).to be(false)
  end
end
```

Fix mutant expression for null integration test
user
```ruby
# encoding: utf-8

require 'spec_helper'

describe 'null integration' do

  let(:base_cmd) { 'bundle exec mutant -I lib --require test_app "TestApp*"' }

  around do |example|
    Dir.chdir(TestApp.root) do
      example.run
    end
  end

  specify 'it allows to kill mutations' do
    expect(Kernel.system(base_cmd)).to be(false)
  end
end
```
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