5 files changed, 83 insertions, 0 deletions
diff --git a/spec/rubyspec/library/mathn/math/fixtures/classes.rb b/spec/rubyspec/library/mathn/math/fixtures/classes.rb
new file mode 100644
index 0000000000..024732fa7a
--- /dev/null
+++ b/spec/rubyspec/library/mathn/math/fixtures/classes.rb
@@ -0,0 +1,3 @@
+class IncludesMath
+  include Math
+end
diff --git a/spec/rubyspec/library/mathn/math/rsqrt_spec.rb b/spec/rubyspec/library/mathn/math/rsqrt_spec.rb
new file mode 100644
index 0000000000..a49efa6ff9
--- /dev/null
+++ b/spec/rubyspec/library/mathn/math/rsqrt_spec.rb
@@ -0,0 +1,17 @@
+require File.expand_path('../../../../spec_helper', __FILE__)
+
+ruby_version_is ''...'2.5' do
+  require File.expand_path('../shared/rsqrt', __FILE__)
+
+  describe "Math#rsqrt" do
+    it_behaves_like :mathn_math_rsqrt, :_, IncludesMath.new
+
+    it "is a private instance method" do
+      IncludesMath.should have_private_instance_method(:rsqrt)
+    end
+  end
+
+  describe "Math.rsqrt" do
+    it_behaves_like :mathn_math_rsqrt, :_, Math
+  end
+end
diff --git a/spec/rubyspec/library/mathn/math/shared/rsqrt.rb b/spec/rubyspec/library/mathn/math/shared/rsqrt.rb
new file mode 100644
index 0000000000..68e2f7d02f
--- /dev/null
+++ b/spec/rubyspec/library/mathn/math/shared/rsqrt.rb
@@ -0,0 +1,21 @@
+require 'mathn'
+require File.expand_path('../../fixtures/classes', __FILE__)
+
+describe :mathn_math_rsqrt, shared: true do
+  it "returns the square root for Rational numbers" do
+    @object.send(:rsqrt, Rational(9, 25)).should == Rational(3, 5)
+    @object.send(:rsqrt, 16/64).should == Rational(1, 2)
+  end
+
+  it "returns the square root for positive numbers" do
+    @object.send(:rsqrt, 1).should == 1
+    @object.send(:rsqrt, 4.0).should == 2.0
+    @object.send(:rsqrt, 12.34).should == Math.sqrt!(12.34)
+  end
+
+  it "raises an Math::DomainError if the argument is a negative number" do
+    lambda { @object.send(:rsqrt, -1) }.should raise_error(Math::DomainError)
+    lambda { @object.send(:rsqrt, -4.0) }.should raise_error(Math::DomainError)
+    lambda { @object.send(:rsqrt, -16/64) }.should raise_error(Math::DomainError)
+  end
+end
diff --git a/spec/rubyspec/library/mathn/math/shared/sqrt.rb b/spec/rubyspec/library/mathn/math/shared/sqrt.rb
new file mode 100644
index 0000000000..6aab25fc5d
--- /dev/null
+++ b/spec/rubyspec/library/mathn/math/shared/sqrt.rb
@@ -0,0 +1,25 @@
+require 'mathn'
+require File.expand_path('../../fixtures/classes', __FILE__)
+
+describe :mathn_math_sqrt, shared: true do
+  it "returns the square root for Rational numbers" do
+    @object.send(:sqrt, Rational(9, 25)).should == Rational(3, 5)
+    @object.send(:sqrt, 16/64).should == Rational(1, 2)
+  end
+
+  it "returns the square root for Complex numbers" do
+    @object.send(:sqrt, Complex(1, 0)).should == 1
+  end
+
+  it "returns the square root for positive numbers" do
+    @object.send(:sqrt, 1).should == 1
+    @object.send(:sqrt, 4.0).should == 2.0
+    @object.send(:sqrt, 12.34).should == Math.sqrt!(12.34)
+  end
+
+  it "returns the square root for negative numbers" do
+    @object.send(:sqrt, -9).should == Complex(0, 3)
+    @object.send(:sqrt, -5.29).should == Complex(0, 2.3)
+    @object.send(:sqrt, -16/64).should == Complex(0, 1/2)
+  end
+end
diff --git a/spec/rubyspec/library/mathn/math/sqrt_spec.rb b/spec/rubyspec/library/mathn/math/sqrt_spec.rb
new file mode 100644
index 0000000000..b723360891
--- /dev/null
+++ b/spec/rubyspec/library/mathn/math/sqrt_spec.rb
@@ -0,0 +1,17 @@
+require File.expand_path('../../../../spec_helper', __FILE__)
+
+ruby_version_is ''...'2.5' do
+  require File.expand_path('../shared/sqrt', __FILE__)
+
+  describe "Math#rsqrt" do
+    it_behaves_like :mathn_math_sqrt, :_, IncludesMath.new
+
+    it "is a private instance method" do
+      IncludesMath.should have_private_instance_method(:sqrt)
+    end
+  end
+
+  describe "Math.rsqrt" do
+    it_behaves_like :mathn_math_sqrt, :_, Math
+  end
+end