Resolves Add annual adjustments for amountPerAnnum #30

[mancubus77]

Resolves #30

[JDIZM]

Thanks for the contribution @mancubus77 I just made a small suggestion and can you please run prettier and update the unit tests and maybe add an additional test case. Thanks!

[JDIZM]

Nice thanks for the update! Last request from me and I will get it merged in 😃

With the test we want to test the expected output of amountPerAnnum is correct, so ideally we would want to test it changes to the correct amount after the first year. You can use currentPositionInYears to get the balance for a specific year.

You can do something like this:

const firstYearOptions = { ...initialOptions, currentPositionInYears: 1 };
const secondYearOptions = { ...initialOptions, currentPositionInYears: 2 };

const firstYearResult = compoundInterestPerPeriod(firstYearOptions);
const secondYearResult = compoundInterestPerPeriod(secondYearOptions);

Side note: I think I just spotted a previous bug with accrualOfPaymentsPerAnnum: false where the end balance is not updating correctly. I am going to raise an issue and a pr for this.

[JDIZM]

actually I just realised we don't actually return amountPerAnnum to check the output, should we return this amount so we can see what the final contributions would be further down the line?

[JDIZM]

I am going to approve this and we can add this as an additional feature