1 files changed, 91 insertions, 0 deletions
diff --git a/spec/ruby/core/kernel/extend_spec.rb b/spec/ruby/core/kernel/extend_spec.rb
new file mode 100644
index 0000000000..6342d8cae1
--- /dev/null
+++ b/spec/ruby/core/kernel/extend_spec.rb
@@ -0,0 +1,91 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+module KernelSpecs::M
+  def self.extend_object(o)
+    ScratchPad << "extend_object"
+    super
+  end
+
+  def self.extended(o)
+    ScratchPad << "extended"
+    super
+  end
+
+  def self.append_features(o)
+    ScratchPad << "append_features"
+    super
+  end
+end
+
+describe "Kernel#extend" do
+  before :each do
+    ScratchPad.record []
+  end
+
+  it "requires multiple arguments" do
+    Object.new.method(:extend).arity.should < 0
+  end
+
+  it "calls extend_object on argument" do
+    o = mock('o')
+    o.extend KernelSpecs::M
+    ScratchPad.recorded.include?("extend_object").should == true
+  end
+
+  it "does not calls append_features on arguments metaclass" do
+    o = mock('o')
+    o.extend KernelSpecs::M
+    ScratchPad.recorded.include?("append_features").should == false
+  end
+
+  it "calls extended on argument" do
+    o = mock('o')
+    o.extend KernelSpecs::M
+    ScratchPad.recorded.include?("extended").should == true
+  end
+
+  it "makes the class a kind_of? the argument" do
+    c = Class.new do
+      extend KernelSpecs::M
+    end
+    (c.kind_of? KernelSpecs::M).should == true
+  end
+
+  it "raises an ArgumentError when no arguments given" do
+    -> { Object.new.extend }.should raise_error(ArgumentError)
+  end
+
+  it "raises a TypeError when the argument is not a Module" do
+    o = mock('o')
+    klass = Class.new
+    -> { o.extend(klass) }.should raise_error(TypeError)
+  end
+
+  describe "on frozen instance" do
+    before :each do
+      @frozen = Object.new.freeze
+      @module = KernelSpecs::M
+    end
+
+    it "raises an ArgumentError when no arguments given" do
+      -> { @frozen.extend }.should raise_error(ArgumentError)
+    end
+
+    it "raises a FrozenError" do
+      -> { @frozen.extend @module }.should raise_error(FrozenError)
+    end
+  end
+
+  it "updated class methods of a module when it extends self and includes another module" do
+    a = Module.new do
+      extend self
+    end
+    b = Module.new do
+      def foo; :foo; end
+    end
+
+    a.include b
+    a.foo.should == :foo
+  end
+end