Extreme Programming in Perl Robert Nagler phần 6 doc

checking, and printing are contained in separate routines. Each routine

is responsible for one and only one behavior.

• The localtime and gmtime calls are now in the correct order. This

defect in the original version only became apparent to me when I

separated the two output lines.

• Argument type validation is consistent, because it has been isolated

into a single routine ( plan arg assert) that is used for all three

parameters. Several new cases are caught. For example, passing undef

to tests or passing both tests and test (deprecated form) is not

allowed.

• Carp::croak unrecognized directive warning is printed once instead of

a warning per unrecognized directive. The check for unrecognized

directives still does not fail fast (croak or die). I would have liked

to correct this, because passing an invalid directives to plan probably

indicates a broken test. However, the broad user base of Test makes

this change infeasible. Somebody may be depending on the behavior

that this is only a warning.

• Two temporary variables (@todo and $x) were eliminated by using a

functional programming style. By avoiding temporary variables, we

simplify algorithms and eliminate ordering dependencies. See the It’s

a SMOP chapter for a longer example of functional programming.

• $planned was eliminated after $ TODO was converted to a reference.

$planned is known as a denormalization, because it can be computed

from another value ($ TODO in this case). Normal form is when data

structures and databases store the sources of all information once and

only once.

• plan print writes a single string. The seven calls print were unnec￾essary duplication. I often use logical operators instead of imperative

statements to avoid the use of temporary variables, which are another

form of duplication (denormalization).

• The return value from plan is better represented as an empty return,

because it handles list and scalar return contexts correctly. This is a

subtle point about return, and it actually involves an interface change.

The following use assigns an empty list:

Copyright c 2004 Robert Nagler

All rights reserved [email protected]

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