1 files changed, 50 insertions, 0 deletions
diff --git a/spec/ruby/shared/enumerator/enum_for.rb b/spec/ruby/shared/enumerator/enum_for.rb
new file mode 100644
index 0000000000..9030ffbd7d
--- /dev/null
+++ b/spec/ruby/shared/enumerator/enum_for.rb
@@ -0,0 +1,50 @@
+describe :enum_for, shared: true do
+  it "is defined in Kernel" do
+    Kernel.method_defined?(@method).should be_true
+  end
+
+  it "returns a new enumerator" do
+    "abc".send(@method).should be_an_instance_of(Enumerator)
+  end
+
+  it "defaults the first argument to :each" do
+    enum = [1,2].send(@method)
+    enum.map { |v| v }.should == [1,2].each { |v| v }
+  end
+
+  it "exposes multi-arg yields as an array" do
+    o = Object.new
+    def o.each
+      yield :a
+      yield :b1, :b2
+      yield [:c]
+      yield :d1, :d2
+      yield :e1, :e2, :e3
+    end
+
+    enum = o.send(@method)
+    enum.next.should == :a
+    enum.next.should == [:b1, :b2]
+    enum.next.should == [:c]
+    enum.next.should == [:d1, :d2]
+    enum.next.should == [:e1, :e2, :e3]
+  end
+
+  it "uses the passed block's value to calculate the size of the enumerator" do
+    Object.new.enum_for { 100 }.size.should == 100
+  end
+
+  it "defers the evaluation of the passed block until #size is called" do
+    ScratchPad.record []
+
+    enum = Object.new.enum_for do
+      ScratchPad << :called
+      100
+    end
+
+    ScratchPad.recorded.should be_empty
+
+    enum.size
+    ScratchPad.recorded.should == [:called]
+  end
+end