1 files changed, 76 insertions, 0 deletions
diff --git a/spec/ruby/core/integer/bit_length_spec.rb b/spec/ruby/core/integer/bit_length_spec.rb
new file mode 100644
index 0000000000..9a2065af33
--- /dev/null
+++ b/spec/ruby/core/integer/bit_length_spec.rb
@@ -0,0 +1,76 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+
+describe "Integer#bit_length" do
+  context "fixnum" do
+    it "returns the position of the leftmost bit of a positive number" do
+      0.bit_length.should == 0
+      1.bit_length.should == 1
+      2.bit_length.should == 2
+      3.bit_length.should == 2
+      4.bit_length.should == 3
+      n = fixnum_max.bit_length
+      fixnum_max[n].should == 0
+      fixnum_max[n - 1].should == 1
+
+      0.bit_length.should == 0
+      1.bit_length.should == 1
+      0xff.bit_length.should == 8
+      0x100.bit_length.should == 9
+      (2**12 - 1).bit_length.should == 12
+      (2**12).bit_length.should == 13
+      (2**12 + 1).bit_length.should == 13
+    end
+
+    it "returns the position of the leftmost 0 bit of a negative number" do
+      -1.bit_length.should == 0
+      -2.bit_length.should == 1
+      -3.bit_length.should == 2
+      -4.bit_length.should == 2
+      -5.bit_length.should == 3
+      n = fixnum_min.bit_length
+      fixnum_min[n].should == 1
+      fixnum_min[n - 1].should == 0
+
+      (-2**12 - 1).bit_length.should == 13
+      (-2**12).bit_length.should == 12
+      (-2**12 + 1).bit_length.should == 12
+      -0x101.bit_length.should == 9
+      -0x100.bit_length.should == 8
+      -0xff.bit_length.should == 8
+      -2.bit_length.should == 1
+      -1.bit_length.should == 0
+    end
+  end
+
+  context "bignum" do
+    it "returns the position of the leftmost bit of a positive number" do
+      (2**1000-1).bit_length.should == 1000
+      (2**1000).bit_length.should == 1001
+      (2**1000+1).bit_length.should == 1001
+
+      (2**10000-1).bit_length.should == 10000
+      (2**10000).bit_length.should == 10001
+      (2**10000+1).bit_length.should == 10001
+
+      (1 << 100).bit_length.should == 101
+      (1 << 100).succ.bit_length.should == 101
+      (1 << 100).pred.bit_length.should == 100
+      (1 << 10000).bit_length.should == 10001
+    end
+
+    it "returns the position of the leftmost 0 bit of a negative number" do
+      (-2**10000-1).bit_length.should == 10001
+      (-2**10000).bit_length.should == 10000
+      (-2**10000+1).bit_length.should == 10000
+
+      (-2**1000-1).bit_length.should == 1001
+      (-2**1000).bit_length.should == 1000
+      (-2**1000+1).bit_length.should == 1000
+
+      ((-1 << 100)-1).bit_length.should == 101
+      ((-1 << 100)-1).succ.bit_length.should == 100
+      ((-1 << 100)-1).pred.bit_length.should == 101
+      ((-1 << 10000)-1).bit_length.should == 10001
+    end
+  end
+end