This is normal JS behaviour. Object equality is by reference, not by value.

The test 'should return correct result even for objects as arguments' doesn't work properly. This description confused me.

param1 = {foo: 'foo', bar: 'bar'};
param2 = {bar: 'bar', foo: 'foo'};

Object like param1 and param2 should be cashed like identical parameters because they have the same keys and values. But the test counts these objects like differnt parameters.