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perfect_spec.rb
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perfect_spec.rb
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require File.expand_path(File.dirname(__FILE__) + '/spec_helper')
describe Integer, "#perfect?" do
it "returns true for the first 7 perfect numbers" do
[6, 28, 496, 8128, 33550336, 8589869056, 137438691328].each do |n|
n.perfect?.should be_true
end
end
it "returns false for the neighbours of the first 7 perfect numbers" do
[6, 28, 496, 8128, 33550336, 8589869056, 137438691328].each do |n|
(n+1).perfect?.should be_false
(n-1).perfect?.should be_false
end
end
it "returns false for odd integers" do
[29,31,33,35].each do |n|
n.perfect?.should be_false
end
end
it "returns false for 1" do
1.perfect?.should be_false
end
it "returns false for 0" do
0.perfect?.should be_false
end
it "returns false for -1" do
-1.perfect?.should be_false
end
it "returns false for non-perfect positive integers" do
[8, 66, 3478].each do |n|
n.perfect?.should be_false
end
end
it "returns false for negative integers" do
-6.perfect?.should be_false
end
end
describe Integer, "#proper_divisors" do
it "returns an Array" do
6.proper_divisors.should be_an_instance_of(Array)
end
it "returns integers that divide into self with no remainder" do
6.proper_divisors.should include(2, 3)
end
it "doesn't return integers that divide into self with a remainder" do
6.proper_divisors.should_not include(4, 5)
end
it "doesn't return itself as a divisor" do
9.proper_divisors.should_not include(9)
end
it "returns all of the proper divisors of self" do
33.proper_divisors.sort.should == [1, 3, 11]
end
it "returns [] for 1" do
1.proper_divisors.should == []
end
it "returns [] for 0" do
0.proper_divisors.should == []
end
it "returns [] for -1" do
-1.proper_divisors.should == []
end
it "returns [] when self is negative" do
-32.proper_divisors.should == []
end
end
describe Integer, "#digital_root" do
it "returns each single-digit number as is" do
(0..9).each do |n|
n.digital_root.should == n
end
end
it "returns the sum of the digits of multi-digit numbers" do
18.digital_root.should == 9
end
it "returns a single digit even when the sum of the digits is greater than 9" do
65536.digital_root.should == 7
end
it "works for negative numbers" do
-4.digital_root.should == 5
-99.digital_root.should == 9
end
end