None of the people who understand the meaning of electronics does not argue with this opinion, it's true, but as correctly observed by dear rsjsouza - the key purpose for this project is a QUICK TEST of a part, removed from the board or a new (unknown) part. For more detailed testing and analysis you will certainly need more serious equipment.
I agree 100%.The transistor tester is intended to be the quickest, easiest, and lowest cost method to identify unknown components and provide reasonable measurements of their parameters. Often this is sufficient when diagnosing a malfunctioning circuit. Faulty components usually measure grossly out of spec. But a component which measures within +/- 20% of its expected value is likely to be functional.
Yes, "lab grade" test gear can be necessary for comprehensive design and debugging projects. However one doesn't
always need expensive gear to quickly determine whether a component is good or bad. I own plenty of test gear, yet I nearly always make my "first tests" with small convenient easy-to-use tools like the transistor tester or a hand-held 3.5 digit multimeter. I also own a 6.5 digit multimeter ( HP 3456A ), but I don't use it every day.
Finally, for people with limited budgets and for folks who are just starting out with electronics, low-cost multi-function test gear like the transistor tester is essential.