Why is Minitest so slow?

Minitest is taking 52 seconds to run 3 tests, can you help me diagnose and correct the delay:

time bin/rake test
Running via Spring preloader in process 6302
Run options: --seed 53674

# Running:

...

Finished in 0.981134s, 3.0577 runs/s, 3.0577 assertions/s.

3 runs, 3 assertions, 0 failures, 0 errors, 0 skips


real    0m52.954s
user    0m0.431s
sys 0m0.148s