Add boot time duration reporting

[tjchambers]

I propose that the duration from initiating mutant (hitting return) until mutant begins the killing processes be measured and added to the reporting output.

My reason is that for me it is excessive (about 15 seconds) and unknown whether it is constant, nor how I can influence it. If it was measured than I could evaluate it across all of my various usages, and also try to speed it up. I doubt it is directly attributable to mutant code, but rather to Rails and project size, number of specs, etc.

I am dealing with a large Rails project targeting mutation testing (currently) on my models. I have almost 4000 examples, but only a handful apply to any one model on average.

If I can adjust the autoloading and restrict specs, I may be able to get that one-time per cycle down which would pay big dividends.

What is measured, improves.

[mbj]

I like this idea and support this feature request. Also please note: Mutant tries to do as much work as possible on boot. to reduce the work done by mutation. Resulting in faster kills.

So mutant trades a longer boot for faster kills intentionally.

I totally agree that mutant should report the boot progress, with timings to problems / improvements are easier to find / debug.

[mbj]

Mutant now got a noticable boot speed bump: https://github.com/mbj/mutant/pull/1276/files

[mbj]

Another, much more significant boot speed bump: https://github.com/mbj/mutant/blob/main/Changelog.md#v01114-2022-07-31