Just to provide a bit more background information to my question. When I run the test of one of the examples provided by the book, I get the following output:
# Running tests:
Finished tests in 0.111129s, 44.9928 tests/s, 206.9667 assertions/s.
5 tests, 23 assertions, 0 failures, 0 errors, 0 skips
Whereas the book shows the following output:
Loaded suite lib/rake/rake_test_loader
PASS product attributes must not be empty (0.23s)
Finished in 0.231576 seconds.
1 tests, 5 assertions, 0 failures, 0 errors, 0 skips
Maybe the different output is caused by changes in rails or ruby itself or by some options. I am just starting out with ruby/rails and would really like to have a bit more details when running tests.