payerEmail attribute is null when options undefined.
payerEmail attribute is null when requestPayerEmail is undefined.
payerEmail attribute is null when requestPayerEmail is false.
payerEmail attribute is 'wpt@w3.org' when requestPayerEmail is true.
payerEmail attribute is 'wpt@w3.org' when requestPayerEmail is truthy.

PASS Can construct a payment request (smoke test). 
PASS payerEmail attribute is null when options undefined. 
PASS payerEmail attribute is null when requestPayerEmail is undefined. 
PASS payerEmail attribute is null when requestPayerEmail is false. 
PASS payerEmail attribute is 'wpt@w3.org' when requestPayerEmail is true. 
PASS payerEmail attribute is 'wpt@w3.org' when requestPayerEmail is truthy.