Add test to example rpc extension

[ckoopmann]

closes #4868

[codecov]

Codecov Report

Merging #4872 (aeeabab) into main (858ea41) will decrease coverage by 51.72%.
The diff coverage is n/a.

❗ Current head aeeabab differs from pull request most recent head 04e995c. Consider uploading reports for the commit 04e995c to get more accurate results

see 400 files with indirect coverage changes

Flag	Coverage Δ
integration-tests	15.51% <ø> (-0.01%)	⬇️
unit-tests	?

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Components	Coverage Δ
reth binary	6.31% <ø> (-25.96%)	⬇️
blockchain tree	0.00% <ø> (-80.45%)	⬇️
pipeline	0.00% <ø> (-88.46%)	⬇️
storage (db)	16.40% <ø> (-56.90%)	⬇️
trie	0.00% <ø> (-94.53%)	⬇️
txpool	23.15% <ø> (-25.88%)	⬇️
networking	24.78% <ø> (-51.43%)	⬇️
rpc	24.88% <ø> (-32.90%)	⬇️
consensus	0.92% <ø> (-60.15%)	⬇️
revm	1.32% <ø> (-27.21%)	⬇️
payload builder	8.16% <ø> (ø)
primitives	19.64% <ø> (-65.63%)	⬇️

[mattsse]

lgtm!

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