spec/ruby/core/enumerator/peek_spec.rb


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require File.expand_path('../../../spec_helper', __FILE__)

describe "Enumerator#peek" do
  before :each do
    @e = (1..5).to_a.to_enum
  end

  it "returns the next element in self" do
    @e.peek.should == 1
  end

  it "does not advance the position of the current element" do
    @e.next.should == 1
    @e.peek.should == 2
    @e.next.should == 2
  end

  it "can be called repeatedly without advancing the position of the current element" do
    @e.peek
    @e.peek
    @e.peek.should == 1
    @e.next.should == 1
  end

  it "works in concert with #rewind" do
    @e.next
    @e.next
    @e.rewind
    @e.peek.should == 1
  end

  it "raises StopIteration if called on a finished enumerator" do
    5.times { @e.next }
    lambda { @e.peek }.should raise_error(StopIteration)
  end
end