implement: src/testing -- #[test], assert!, integration tests with real data

[BryanChasko]

topic: testing

rust has first-class test support built into cargo.

concepts to demonstrate

• #[test] attribute
• assert!, assert_eq!, assert_ne!
• #[should_panic] for expected failures
• #[cfg(test)] module pattern
• integration tests in tests/ directory
• doc tests in /// comments

patriots theme

unit tests for passer_rating() against brady's known 2004 stats.
integration test loading real CSV data from datasets/ and asserting totals.

files

src/testing/test_helpers.rs
tests/integration_stats.rs

reference

python mirror: basic_test_calculator.py, basic_test_hello.py