Add example test

[komuw]

What(What have you changed/added/removed?)

• Add example test

Why(Why did you change/add/remove it?)

[codecov-io]

Codecov Report

Merging #13 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #13   +/-   ##
=======================================
  Coverage   92.96%   92.96%           
=======================================
  Files           3        3           
  Lines         256      256           
=======================================
  Hits          238      238           
  Misses         14       14           
  Partials        4        4           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 31c6ae7...3f2844f. Read the comment docs.

[komuw]

This is kind of blocked on;

1. testing: show diffs for incorrect output from Example tests golang/go#41980
2. cmd/gofmt: reformats block comments golang/go#5128 (comment)