Test::MockRandom(3pm)					User Contributed Perl Documentation				     Test::MockRandom(3pm)

NAME

       Test::MockRandom -  Replaces random number generation with non-random number generation

VERSION

       This documentation describes version 1.00.

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:

       o   String: a package to which Test::MockRandom will export the symbol

       o   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

       o   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.

BUGS

       Please report any bugs or feature requests using the CPAN Request Tracker.  Bugs can be submitted through the web interface at
       <http://rt.cpan.org/Dist/Display.html?Queue=Test::MockRandom>

       When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired
       feature.

SEE ALSO

       o   Test::MockObject

       o   Test::MockModule

AUTHOR

       David A. Golden (DAGOLDEN)

COPYRIGHT AND LICENSE

       Copyright (c) 2004-2007 by David A. Golden

       Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.  You may
       obtain a copy of the License at <http://www.apache.org/licenses/LICENSE-2.0>

       Files produced as output though the use of this software, shall not be considered Derivative Works, but shall be considered the original
       work of the Licensor.

       Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS,
       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the specific language governing permissions
       and limitations under the License.

perl v5.10.0							    2007-12-17						     Test::MockRandom(3pm)