Merge pull request #1344 from puppetlabs/seeded_rand

Rewrite seeded_rand() as a Puppet 4.x function

Author: binford2k

lib/puppet/functions/seeded_rand.rb

@@ -0,0 +1,22 @@
+# 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

lib/puppet/parser/functions/seeded_rand.rb

@@ -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