Mindshare is a term I rarely hear outside of business or technology magazines, but is very appropriate here. Java has long been king in the unit testing space, and though hoary, JUnit is still one of the best unit testing libraries around.
In the 90s the evolving Java ecosystem was the top reason I moved from C/C++ to Java. JDK7 looks to keep Java the language on life support so it will not immediate wither away (although who came up with the name public defender methods [PDF]?). But the library momentum is not in Java's favor at the moment.