Well, for 3D games it's a huge process, can easily take 100 designers to make a game these days, that be on medium scaled games, on the huge ..uuhhhh!!
Browser based games, doesn't take that much, many can graphicly be designed in 2D based drawing programs, dunno much about the programming though, but I think even the simplest of windows Notepad will do.
Test phase, your cude game must enter an "Alpha stage", for test the core idea, which ideas to evolve, and which to slash ..etc.
Beta state, early, mid and late: Balancing, finding errors in code, design ..optimizing ..optimizing!!
Then there's the publication, you must have some to make marketing and ads.