Tests migrated to ES6

[KoolTheba]

Main changes

• Migrated test code base to ES6
• Reduced redundancy
• Removed unused dependencies

Context

Related to #218

Changelog

• 582e731 WIP.Test refactor by @KoolTheba
  • ES6 refactor for test-manifest
  • Removed unused callbacks in test
  • Reduced test redundancy
• 857ccb6 WIP.Test refactor by @KoolTheba
  • ES6 refactor for test-generator
  • pkgContainsDevDependencies has been removed
• 135585d WIP.Test refactor by @KoolTheba
• fc2fee0 Test refactor by @KoolTheba
  • ES6 refactor for helper
  • Removed dependency object-assign