This was because should wasn't defined in that context and was referring
to should property of the global object which is from the prototype.
So should.exist and should.not.exist were undefined, which made
stackStartFunction properties in those functions undefined.
This was because should wasn't defined in that context and was referring to should property of the
global
object which is from the prototype. Soshould.exist
andshould.not.exist
were undefined, which made stackStartFunction properties in those functions undefined.