smallerEq(): Less Than or Equal To
smallerEq() tests an inclusive upper bound. It returns true when the first value is less than or equal to the second, making it useful for limits and allowed ranges.
Inclusive comparisons
Use smaller() when equality should fail and largerEq() for a closed lower bound. Combine tests with and() to validate a range.
Ensure units are comparable, using to() where necessary. For calculated decimals, establish a tolerance instead of relying on formatting.