practice vs proving ground

practice

noun
  • Actual operation or experiment, in contrast to theory. 

  • A customary action, habit, or behaviour; a manner or routine. 

  • The ongoing pursuit of a craft or profession, particularly in medicine or the fine arts. 

  • A place where a professional service is provided, such as a general practice. 

  • The observance of religious duties that a church requires of its members. 

  • An organized event for the purpose of performing such repetition. 

  • The form, manner, and order of conducting and carrying on suits and prosecutions through their various stages, according to the principles of law and the rules laid down by the courts. 

  • Skilful or artful management; dexterity in contrivance or the use of means; stratagem; artifice. 

  • Repetition of an activity to improve a skill. 

  • A easy and concise method of applying the rules of arithmetic to questions which occur in trade and business. 

proving ground

noun
  • A venue or project in which new technologies, methods, or techniques are tested. 

  • A terrain or installation for testing weapons, military equipment, or tactics. 

How often have the words practice and proving ground occurred in a corpus of books? (source: Google Ngram Viewer )