Clarify (misleading?) bit about parallelism and credit usage in Test Splitting Tutorial

[tony-pizza]

Location

• https://circleci.com/docs/test-splitting-tutorial/
• https://github.com/circleci/circleci-docs/blob/881833257eb31528899955b537070d5a1cf63c08/jekyll/_cci2/test-splitting-tutorial.adoc

Explanation

This is based on the following assumption:

• When using parallelism, CircleCI bills for sum total compute time (e.g. 2 parallel runs at 5min counts as 10min of credit usage)

If this assumption is incorrect, please let me know!

Tutorial states you will:

See how test splitting can help decrease pipeline run times and optimize credit usage.

However, I don't feel that the Test Splitting Tutorial really explains how test splitting optimizes credit usage. And, in fact, I believe test splitting would typically increase credit usage, as each parallel run would spend some time doing some test setup or initialization.

Am I missing something here?