David Wilson provides an introduction to Pester:
Most of you probably know that I’m a big fan of automated testing and especially testing during the development process. It significantly improves the design of the code by encouraging loose coupling and high cohesion. It also provides great documentation and increases the confidence of anyone who needs to change the code in the future (this includes future you)!
Testing does tend to get the short end of the stick when it comes to development time. Some of that is design problems, like David mentions, but I think a lot of it is the “This is a solved problem” mentality we (and I am definitely part of “we” here) end up in: I proved that the solution work because the code compiled and the two scenarios I tried out worked; therefore, why do I need to “waste” the extra time by writing all of these tests when I can move on to something more interesting?