1 files changed, 69 insertions, 0 deletions
diff --git a/spec/ruby/core/integer/gcd_spec.rb b/spec/ruby/core/integer/gcd_spec.rb
new file mode 100644
index 0000000000..961f1c5c2e
--- /dev/null
+++ b/spec/ruby/core/integer/gcd_spec.rb
@@ -0,0 +1,69 @@
+require_relative '../../spec_helper'
+
+describe "Integer#gcd" do
+  it "returns self if equal to the argument" do
+    1.gcd(1).should == 1
+    398.gcd(398).should == 398
+  end
+
+  it "returns an Integer" do
+    36.gcd(6).should be_kind_of(Integer)
+    4.gcd(20981).should be_kind_of(Integer)
+  end
+
+  it "returns the greatest common divisor of self and argument" do
+    10.gcd(5).should == 5
+    200.gcd(20).should == 20
+  end
+
+  it "returns a positive integer even if self is negative" do
+    -12.gcd(6).should == 6
+    -100.gcd(100).should == 100
+  end
+
+  it "returns a positive integer even if the argument is negative" do
+    12.gcd(-6).should == 6
+    100.gcd(-100).should == 100
+  end
+
+  it "returns a positive integer even if both self and argument are negative" do
+    -12.gcd(-6).should == 6
+    -100.gcd(-100).should == 100
+  end
+
+  it "accepts a Bignum argument" do
+    bignum = 9999**99
+    bignum.should be_kind_of(Integer)
+    99.gcd(bignum).should == 99
+  end
+
+  it "works if self is a Bignum" do
+    bignum = 9999**99
+    bignum.should be_kind_of(Integer)
+    bignum.gcd(99).should == 99
+  end
+
+  it "doesn't cause an integer overflow" do
+    [2 ** (1.size * 8 - 2), 0x8000000000000000].each do |max|
+      [max - 1, max, max + 1].each do |num|
+        num.gcd(num).should == num
+        (-num).gcd(num).should == num
+        (-num).gcd(-num).should == num
+        num.gcd(-num).should == num
+      end
+    end
+  end
+
+  it "raises an ArgumentError if not given an argument" do
+    -> { 12.gcd }.should raise_error(ArgumentError)
+  end
+
+  it "raises an ArgumentError if given more than one argument" do
+    -> { 12.gcd(30, 20) }.should raise_error(ArgumentError)
+  end
+
+  it "raises a TypeError unless the argument is an Integer" do
+    -> { 39.gcd(3.8)   }.should raise_error(TypeError)
+    -> { 45872.gcd([]) }.should raise_error(TypeError)
+  end
+end