Add Hatchet test

spec/hatchet/python_spec.rb

@@ -1,10 +1,28 @@
 require_relative '../spec_helper'
 
-describe "Python!!!!!!!!!!!" do
+describe "Default Python Deploy" do
   it "🐍" do
     Hatchet::Runner.new('python-getting-started', stack: DEFAULT_STACK).deploy do |app|
       expect(app.output).to           match(/Installing pip/)
       expect(app.run('python -V')).to match(/3.6.10/)
+
+
+      expect(app.output).to_not match("Clearing cached dependencies")
+
+      # Redeploy
+      run!(%Q{echo "flask" >> requirements.txt})
+      run!(%Q{git add . ; git commit --allow-empty -m next})
+      app.push!
+
+      # Check for the cache tohave cleared
+      expect(app.output).to match("Clearing cached dependencies")
+
+      run!(%Q{git commit --allow-empty -m next})
+      app.push!
+
+      # The cache should not clear with no changes
+      expect(app.output).to_not match("Clearing cached dependencies")
+
     end
   end
 end

spec/spec_helper.rb

@@ -20,4 +20,10 @@ if ENV['TRAVIS']
   exit 0 if ENV['TRAVIS_PULL_REQUEST'] != 'false' && ENV['TRAVIS_BRANCH'] == 'master'
 end
 
-DEFAULT_STACK = 'heroku-16'
+DEFAULT_STACK = 'heroku-18'
+
+def run!(cmd)
+  out = `#{cmd}`
+  raise "Error running command #{cmd} with output: #{out}" unless $?.success?
+  return out
+end