Jest gives you a streamlined, text-based interface. You can type in a single number and get single answer. With a little more information, you can get a more find-grained answer.

Basic Use

Suppose you have six months. From the command line, run:

$ jest 6

which outputs:

1.5E+03 lines    (from 3.8E+02 to 6.1E+03)

This means that you can afford about four hundred to six thousand lines of code. You may be able to write much more than that, but then you’ll probably run out of time for testing, debugging, and confirming that anyone wants what you’ve written.

Six thousand represents the high end of a range. Even people who are unusually fast testers and debuggers would be rushing (or leaving in a lot of bugs). Four hundred is the low end, where you can comfortably deliver high quality, and one thousand five hundred is the most typical figure from within the range.

If your available time is not phrased in terms of months, you can use several other time units:

$ jest --time-units hours 1000
2E+03 lines    (from 5E+02 to 8E+03)

The input number is actually considered a floating point:

$ jest 7.5
2.9E+03 lines    (from 7.2E+02 to 1.2E+04)
$ jest --time-units hours 1e3
2E+03 lines    (from 5E+02 to 8E+03)