Need computer science help to Describe and discuss maintenance testing, when it occurs and why it is important

Describe and discuss maintenance testing, when it occurs and why it is important.       post an original thread of 100 to 150 wordsNote : Need each question in separate document and need original content with citations and referneces . no plagarismPlease it is urjunt need it in 2 hours , i need 150 words , wth references and original content no plagarism please .