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Rewrite seeded_rand() as a Puppet 4.x function #1344

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May 4, 2023
Merged

Rewrite seeded_rand() as a Puppet 4.x function #1344

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607b684
Rework the tests to check actual values
smortex Apr 28, 2023
2050371
Rewrite seeded_rand() as a Puppet 4.x function
smortex Apr 28, 2023
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22 changes: 22 additions & 0 deletions lib/puppet/functions/seeded_rand.rb
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# frozen_string_literal: true

# @summary
# Generates a random whole number greater than or equal to 0 and less than max, using the value of seed for repeatable randomness.
Puppet::Functions.create_function(:seeded_rand) do
# @param max The maximum value.
# @param seed The seed used for repeatable randomness.
#
# @return [Integer]
# A random number greater than or equal to 0 and less than max
dispatch :seeded_rand do
param 'Integer[1]', :max
param 'String', :seed
end

def seeded_rand(max, seed)
require 'digest/md5'

seed = Digest::MD5.hexdigest(seed).hex
Puppet::Util.deterministic_rand_int(seed, max)
end
end
30 changes: 0 additions & 30 deletions lib/puppet/parser/functions/seeded_rand.rb
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69 changes: 17 additions & 52 deletions spec/functions/seeded_rand_spec.rb
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Expand Up @@ -4,57 +4,22 @@

describe 'seeded_rand' do
it { is_expected.not_to eq(nil) }
it { is_expected.to run.with_params.and_raise_error(ArgumentError, %r{wrong number of arguments}i) }
it { is_expected.to run.with_params(1).and_raise_error(ArgumentError, %r{wrong number of arguments}i) }
it { is_expected.to run.with_params(0, '').and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
it { is_expected.to run.with_params(1.5, '').and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
it { is_expected.to run.with_params(-10, '').and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
it { is_expected.to run.with_params('-10', '').and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
it { is_expected.to run.with_params('string', '').and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
it { is_expected.to run.with_params([], '').and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
it { is_expected.to run.with_params({}, '').and_raise_error(ArgumentError, %r{first argument must be a positive integer}) }
it { is_expected.to run.with_params(1, 1).and_raise_error(ArgumentError, %r{second argument must be a string}) }
it { is_expected.to run.with_params(1, []).and_raise_error(ArgumentError, %r{second argument must be a string}) }
it { is_expected.to run.with_params(1, {}).and_raise_error(ArgumentError, %r{second argument must be a string}) }

it 'provides a random number strictly less than the given max' do
expect(seeded_rand(3, 'seed')).to satisfy { |n| n.to_i < 3 } # rubocop:disable Lint/AmbiguousBlockAssociation : Cannot parenthesize without break code or violating other Rubocop rules
end

it 'provides a random number greater or equal to zero' do
expect(seeded_rand(3, 'seed')).to satisfy { |n| n.to_i >= 0 } # rubocop:disable Lint/AmbiguousBlockAssociation : Cannot parenthesize without break code or violating other Rubocop rules
end

it "provides the same 'random' value on subsequent calls for the same host" do
expect(seeded_rand(10, 'seed')).to eql(seeded_rand(10, 'seed'))
end

it 'allows seed to control the random value on a single host' do
first_random = seeded_rand(1000, 'seed1')
second_different_random = seeded_rand(1000, 'seed2')

expect(first_random).not_to eql(second_different_random)
end

it 'does not return different values for different hosts' do
val1 = seeded_rand(1000, 'foo', host: 'first.host.com')
val2 = seeded_rand(1000, 'foo', host: 'second.host.com')

expect(val1).to eql(val2)
end

def seeded_rand(max, seed, args = {})
host = args[:host] || '127.0.0.1'

# workaround not being able to use let(:facts) because some tests need
# multiple different hostnames in one context
allow(scope).to receive(:lookupvar).with('::fqdn', {}).and_return(host)

scope.function_seeded_rand([max, seed])
end

context 'with UTF8 and double byte characters' do
it { is_expected.to run.with_params(1000, 'ǿňè') }
it { is_expected.to run.with_params(1000, '文字列') }
it { is_expected.to run.with_params.and_raise_error(ArgumentError, %r{'seeded_rand' expects 2 arguments, got none}i) }
it { is_expected.to run.with_params(1).and_raise_error(ArgumentError, %r{'seeded_rand' expects 2 arguments, got 1}i) }
it { is_expected.to run.with_params(0, '').and_raise_error(ArgumentError, %r{parameter 'max' expects an Integer\[1\] value, got Integer\[0, 0\]}) }
it { is_expected.to run.with_params(1.5, '').and_raise_error(ArgumentError, %r{parameter 'max' expects an Integer value, got Float}) }
it { is_expected.to run.with_params(-10, '').and_raise_error(ArgumentError, %r{parameter 'max' expects an Integer\[1\] value, got Integer\[-10, -10\]}) }
it { is_expected.to run.with_params('string', '').and_raise_error(ArgumentError, %r{parameter 'max' expects an Integer value, got String}) }
it { is_expected.to run.with_params([], '').and_raise_error(ArgumentError, %r{parameter 'max' expects an Integer value, got Array}) }
it { is_expected.to run.with_params({}, '').and_raise_error(ArgumentError, %r{parameter 'max' expects an Integer value, got Hash}) }
it { is_expected.to run.with_params(1, 1).and_raise_error(ArgumentError, %r{parameter 'seed' expects a String value, got Integer}) }
it { is_expected.to run.with_params(1, []).and_raise_error(ArgumentError, %r{parameter 'seed' expects a String value, got Array}) }
it { is_expected.to run.with_params(1, {}).and_raise_error(ArgumentError, %r{parameter 'seed' expects a String value, got Hash}) }

context 'produce predictible and reproducible results' do
it { is_expected.to run.with_params(20, 'foo').and_return(1) }
it { is_expected.to run.with_params(100, 'bar').and_return(35) }
it { is_expected.to run.with_params(1000, 'ǿňè').and_return(247) }
it { is_expected.to run.with_params(1000, '文字列').and_return(67) }
end
end