Add unit test for net_amount when fee_amount is set

[eileenmcnaughton]

Overview

This just improves testing & ensures fee_amount is used to set net amount.

I got some odd results on financial_trxn & financial_item but just adding checks for
what I found atm

Before

Less tests, net_amount not calculated off fee_amount

After

More tests, net_amount calculated

Technical Details

Preliminary digging towards eileenmcnaughton/nz.co.fuzion.omnipaymultiprocessor#127

Comments

@mattwire I think this was something you were trying to tell me about - even though we say processors should only set fee_amount in this scenario that wasn't enough & without this patch they need to set net_amount too

[civibot]

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[seamuslee001]

This looks good to me adding MOP

[mattwire]

@eileenmcnaughton Yes, total_amount, fee_amount, tax_amount should all be "settable", net_amount should always be calculated so should never be set explicitly