Heatmap graph - test may be off by one

Test number 8:

The “data-month”, “data-year” of each cell should be within the range of the data.

var t=+e.getAttribute("data-month");
o.assert.isAtLeast(t,0,"data-month should be at least 0"),
o.assert.isAtMost(t,11,"data-month should be at most 11")}

Range of test is 0 - 11.
Range of data.month is 1 - 12.

Don’t know if it is intended. If so, lock/delete this thread.

My proposal (if not intended): increase upper bound by one, so it will be backward compatible.