Why are assertEquals() parameters in the order (expected, actual)?

Question

Why do so many assertEquals() or similar function take the expected value as first parameter and the actual one as second ?
This seems counter-intuitive to me,

Answer 1

The xUnit testing convention is expected/actual. So, for many that is the natural order since that's what they learnt.

Interestingly in a break from convention for an xUnit framework qunit goes for actual/expected. At least with javascript you can just create a new function that encapsulates the old one and assign it the original variable:

var qunitEquals = equals;
equals = function(expected, actual, message) {
    qunitEquals(actual, expected, message);
};