Confirm the relayer gets paid rewards in unit tests

[alistair-singh]

Resolves: SNO-807

paritytech/polkadot-sdk#2522 (comment)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c481b54) 80.69% compared to head (7f54f39) 80.69%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1081   +/-   ##
=======================================
  Coverage   80.69%   80.69%           
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  Files          55       55           
  Lines        2274     2274           
  Branches       71       71           
=======================================
  Hits         1835     1835           
  Misses        422      422           
  Partials       17       17           

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[Lederstrumpf]

Suggested change

	let reward = Parameters::get().rewards.local;
	assert!(Balances::balance(&relayer) >= reward, "relayer was rewarded");
	assert!(
	Balances::balance(&channel_sovereign) <= initial_fund - reward,
	"sovereign account paid reward"
	);
	let delivery_cost = InboundQueue::calculate_delivery_cost(message.encode().len() as u32);
	assert!(Parameters::get().rewards.local < delivery_cost, "delivery cost exceeds pure reward");
	assert_eq!(Balances::balance(&relayer), delivery_cost, "relayer was reimbursed and rewarded");
	assert!(
	Balances::balance(&channel_sovereign) <= initial_fund - delivery_cost,
	"sovereign account paid reward and delivery fee"
	);

[alistair-singh]

Addressed in #1086