Issue:
Without that sleep 0.1 - this test fails more often than passes.
With the sleep if passes every time.

### test
require 'spec_helper'

RSpec.describe 'testing file writing', :type => :aruba do
  let!(:test_file) { 'out.txt' }
  let!(:directory) { 'test_write' }
  before(:each) {
    setup_aruba
    create_directory(directory)
    set_environment_variable 'TMP_DIR', expand_path(directory)
  }
  it 'should write a file' do
    run 'test_write.bash'
    sleep 0.1
    expect(file?("#{directory}/out.txt")).to be true
  end
end



### test_write.bash
#!/bin/bash
echo hello_world > $TMP_DIR/out.txt


### Gemfile.lock
$ cat Gemfile.lock
GEM
  remote: https://rubygems.org/
  specs:
    aruba (0.9.0)
      childprocess (~> 0.5.6)
      contracts (~> 0.9)
      cucumber (>= 1.3.19)
      ffi (~> 1.9.10)
      rspec-expectations (>= 2.99)
      thor (~> 0.19)
    builder (3.2.2)
    childprocess (0.5.6)
      ffi (~> 1.0, >= 1.0.11)
    coderay (1.1.0)
    contracts (0.12.0)
    cucumber (2.1.0)
      builder (>= 2.1.2)
      cucumber-core (~> 1.3.0)
      diff-lcs (>= 1.1.3)
      gherkin3 (~> 3.1.0)
      multi_json (>= 1.7.5, < 2.0)
      multi_test (>= 0.1.2)
    cucumber-core (1.3.0)
      gherkin3 (~> 3.1.0)
    diff-lcs (1.2.5)
    ffi (1.9.10)
    gherkin3 (3.1.2)
    json (1.8.1)
    method_source (0.8.2)
    multi_json (1.11.2)
    multi_test (0.1.2)
    pry (0.10.3)
      coderay (~> 1.1.0)
      method_source (~> 0.8.1)
      slop (~> 3.4)
    rspec (3.3.0)
      rspec-core (~> 3.3.0)
      rspec-expectations (~> 3.3.0)
      rspec-mocks (~> 3.3.0)
    rspec-core (3.3.2)
      rspec-support (~> 3.3.0)
    rspec-expectations (3.3.1)
      diff-lcs (>= 1.2.0, < 2.0)
      rspec-support (~> 3.3.0)
    rspec-mocks (3.3.2)
      diff-lcs (>= 1.2.0, < 2.0)
      rspec-support (~> 3.3.0)
    rspec-support (3.3.0)
    slop (3.6.0)
    thor (0.19.1)

PLATFORMS
  ruby

DEPENDENCIES
  aruba
  json
  pry
  rspec

BUNDLED WITH
   1.10.6

#ruby
ruby 2.2.3p173