Provided by: libtest-mockrandom-perl_1.01-1_all 
NAME
Test::MockRandom - Replaces random number generation with non-random number generation
VERSION
version 1.01
SYNOPSIS
# intercept rand in another package
use Test::MockRandom 'Some::Other::Package';
use Some::Other::Package; # exports sub foo { return rand }
srand(0.13);
foo(); # returns 0.13
# using a seed list and "oneish"
srand(0.23, 0.34, oneish() );
foo(); # returns 0.23
foo(); # returns 0.34
foo(); # returns a number just barely less than one
foo(); # returns 0, as the seed array is empty
# object-oriented, for use in the current package
use Test::MockRandom ();
my $nrng = Test::MockRandom->new(0.42, 0.23);
$nrng->rand(); # returns 0.42
DESCRIPTION
This perhaps ridiculous-seeming module was created to test routines that manipulate random
numbers by providing a known output from "rand". Given a list of seeds with "srand", it
will return each in turn. After seeded random numbers are exhausted, it will always
return 0. Seed numbers must be of a form that meets the expected output from "rand" as
called with no arguments -- i.e. they must be between 0 (inclusive) and 1 (exclusive).
In order to facilitate generating and testing a nearly-one number, this module exports the
function "oneish", which returns a number just fractionally less than one.
Depending on how this module is called with "use", it will export "rand" to a specified
package (e.g. a class being tested) effectively overriding and intercepting calls in that
package to the built-in "rand". It can also override "rand" in the current package or
even globally. In all of these cases, it also exports "srand" and "oneish" to the current
package in order to control the output of "rand". See "USAGE" for details.
Alternatively, this module can be used to generate objects, with each object maintaining
its own distinct seed array.
USAGE
By default, Test::MockRandom does not export any functions. This still allows object-
oriented use by calling "Test::MockRandom->new(@seeds)". In order for Test::MockRandom to
be more useful, arguments must be provided during the call to "use".
use Test::MockRandom 'Target::Package'
The simplest way to intercept "rand" in another package is to provide the name(s) of the
package(s) for interception as arguments in the "use" statement. This will export "rand"
to the listed packages and will export "srand" and "oneish" to the current package to
control the behavior of "rand". You must "use" Test::MockRandom before you "use" the
target package. This is a typical case for testing a module that uses random numbers:
use Test::More 'no_plan';
use Test::MockRandom 'Some::Package';
BEGIN { use_ok( Some::Package ) }
# assume sub foo { return rand } was imported from Some::Package
srand(0.5)
is( foo(), 0.5, "is foo() 0.5?") # test gives "ok"
If multiple package names are specified, "rand" will be exported to all of them.
If you wish to export "rand" to the current package, simply provide "__PACKAGE__" as the
parameter for "use", or "main" if importing to a script without a specified package. This
can be part of a list provided to "use". All of the following idioms work:
use Test::MockRandom qw( main Some::Package ); # Assumes a script
use Test::MockRandom __PACKAGE__, 'Some::Package';
# The following doesn't interpolate __PACKAGE__ as above, but
# Test::MockRandom will still DWIM and handle it correctly
use Test::MockRandom qw( __PACKAGE__ Some::Package );
use Test::MockRandom %customized
As an alternative to a package name as an argument to "use", Test::MockRandom will also
accept a hash reference with a custom set of instructions for how to export functions:
use Test::MockRandom {
rand => [ Some::Package, {Another::Package => 'random'} ],
srand => { Another::Package => 'seed' },
oneish => __PACKAGE__
};
The keys of the hash may be any of "rand", "srand", and "oneish". The values of the hash
give instructions for where to export the symbol corresponding to the key. These are
interpreted as follows, depending on their type:
• String: a package to which Test::MockRandom will export the symbol
• Hash Reference: the key is the package to which Test::MockRandom will export the
symbol and the value is the name under which it will be exported
• Array Reference: a list of strings or hash references which will be handled as above
Test::MockRandom->export_rand_to()
In order to intercept the built-in "rand" in another package, Test::MockRandom must export
its own "rand" function to the target package before the target package is compiled, thus
overriding calls to the built-in. The simple approach (described above) of providing the
target package name in the "use Test::MockRandom" statement accomplishes this because
"use" is equivalent to a "require" and "import" within a "BEGIN" block. To explicitly
intercept "rand" in another package, you can also call "export_rand_to", but it must be
enclosed in a "BEGIN" block of its own. The explicit form also support function aliasing
just as with the custom approach with "use", described above:
use Test::MockRandom;
BEGIN {Test::MockRandom->export_rand_to('AnotherPackage'=>'random')}
use AnotherPackage;
This "BEGIN" block must not include a "use" statement for the package to be intercepted,
or perl will compile the package to be intercepted before the "export_rand_to" function
has a chance to execute and intercept calls to the built-in "rand". This is very
important in testing. The "export_rand_to" call must be in a separate "BEGIN" block from
a "use" or "use_ok" test, which should be enclosed in a "BEGIN" block of its own:
use Test::More tests => 1;
use Test::MockRandom;
BEGIN { Test::MockRandom->export_rand_to( 'AnotherPackage' ); }
BEGIN { use_ok( 'AnotherPackage' ); }
Given these cautions, it's probably best to use either the simple or custom approach with
"use", which does the right thing in most circumstances. Should additional explicit
customization be necessary, Test::MockRandom also provides "export_srand_to" and
"export_oneish_to".
Overriding "rand" globally: use Test::MockRandom 'CORE::GLOBAL'
This is just like intercepting "rand" in a package, except that you do it globally by
overriding the built-in function in "CORE::GLOBAL".
use Test::MockRandom 'CORE::GLOBAL';
# or
BEGIN { Test::MockRandom->export_rand_to('CORE::GLOBAL') }
You can always access the real, built-in "rand" by calling it explicitly as "CORE::rand".
Intercepting "rand" in a package that also contains a "rand" function
This is tricky as the order in which the symbol table is manipulated will lead to very
different results. This can be done safely (maybe) if the module uses the same rand
syntax/prototype as the system call but offers them up as method calls which resolve at
run-time instead of compile time. In this case, you will need to do an explicit intercept
(as above) but do it after importing the package. I.e.:
use Test::MockRandom 'SomeRandPackage';
use SomeRandPackage;
BEGIN { Test::MockRandom->export_rand_to('SomeRandPackage');
The first line is necessary to get "srand" and "oneish" exported to the current package.
The second line will define a "sub rand" in "SomeRandPackage", overriding the results of
the first line. The third line then re-overrides the "rand". You may see warnings about
"rand" being redefined.
Depending on how your "rand" is written and used, there is a good likelihood that this
isn't going to do what you're expecting, no matter what. If your package that defines
"rand" relies internally upon the system "CORE::GLOBAL::rand" function, then you may be
best off overriding that instead.
FUNCTIONS
"new"
$obj = new( LIST OF SEEDS );
Returns a new Test::MockRandom object with the specified list of seeds.
"srand"
srand( LIST OF SEEDS );
$obj->srand( LIST OF SEEDS);
If called as a bare function call or package method, sets the seed list for bare/package
calls to "rand". If called as an object method, sets the seed list for that object only.
"rand"
$rv = rand();
$rv = $obj->rand();
$rv = rand(3);
If called as a bare or package function, returns the next value from the package seed
list. If called as an object method, returns the next value from the object seed list.
If "rand" is called with a numeric argument, it follows the same behavior as the built-in
function -- it multiplies the argument with the next value from the seed array (resulting
in a random fractional value between 0 and the argument, just like the built-in). If the
argument is 0, undef, or non-numeric, it is treated as if the argument is 1.
Using this with an argument in testing may be complicated, as limits in floating point
precision mean that direct numeric comparisons are not reliable. E.g.
srand(1/3);
rand(3); # does this return 1.0 or .999999999 etc.
"oneish"
srand( oneish() );
if ( rand() == oneish() ) { print "It's almost one." };
A utility function to return a nearly-one value. Equal to ( 2^32 - 1 ) / 2^32. Useful in
"srand" and test functions.
"export_rand_to"
Test::MockRandom->export_rand_to( 'Some::Class' );
Test::MockRandom->export_rand_to( 'Some::Class' => 'random' );
This function exports "rand" into the specified package namespace. It must be called as a
class function. If a second argument is provided, it is taken as the symbol name used in
the other package as the alias to "rand":
use Test::MockRandom;
BEGIN { Test::MockRandom->export_rand_to( 'Some::Class' => 'random' ); }
use Some::Class;
srand (0.5);
print Some::Class::random(); # prints 0.5
It can also be used to explicitly intercept "rand" after Test::MockRandom has been loaded.
The effect of this function is highly dependent on when it is called in the compile cycle
and should usually called from within a BEGIN block. See "USAGE" for details.
Most users will not need this function.
"export_srand_to"
Test::MockRandom->export_srand_to( 'Some::Class' );
Test::MockRandom->export_srand_to( 'Some::Class' => 'seed' );
This function exports "srand" into the specified package namespace. It must be called as
a class function. If a second argument is provided, it is taken as the symbol name to use
in the other package as the alias for "srand". This function may be useful if another
package wraps "srand":
# In Some/Class.pm
package Some::Class;
sub seed { srand(shift) }
sub foo { rand }
# In a script
use Test::MockRandom 'Some::Class';
BEGIN { Test::MockRandom->export_srand_to( 'Some::Class' ); }
use Some::Class;
seed(0.5);
print foo(); # prints "0.5"
The effect of this function is highly dependent on when it is called in the compile cycle
and should usually be called from within a BEGIN block. See "USAGE" for details.
Most users will not need this function.
"export_oneish_to"
Test::MockRandom->export_oneish_to( 'Some::Class' );
Test::MockRandom->export_oneish_to( 'Some::Class' => 'nearly_one' );
This function exports "oneish" into the specified package namespace. It must be called as
a class function. If a second argument is provided, it is taken as the symbol name to use
in the other package as the alias for "oneish". Since "oneish" is usually only used in a
test script, this function is likely only necessary to alias "oneish" to some other name
in the current package:
use Test::MockRandom 'Some::Class';
BEGIN { Test::MockRandom->export_oneish_to( __PACKAGE__, "one" ); }
use Some::Class;
seed( one() );
print foo(); # prints a value very close to one
The effect of this function is highly dependent on when it is called in the compile cycle
and should usually be called from within a BEGIN block. See "USAGE" for details.
Most users will not need this function.
SEE ALSO
• Test::MockObject
• Test::MockModule
SUPPORT
Bugs / Feature Requests
Please report any bugs or feature requests through the issue tracker at
<https://github.com/dagolden/Test-MockRandom/issues>. You will be notified automatically
of any progress on your issue.
Source Code
This is open source software. The code repository is available for public review and
contribution under the terms of the license.
<https://github.com/dagolden/Test-MockRandom>
git clone https://github.com/dagolden/Test-MockRandom.git
AUTHOR
David Golden <dagolden@cpan.org>
COPYRIGHT AND LICENSE
This software is Copyright (c) 2014 by David Golden.
This is free software, licensed under:
The Apache License, Version 2.0, January 2004