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require_relative '../../spec_helper'
describe "Hash#slice" do
before :each do
@hash = { a: 1, b: 2, c: 3 }
end
it "returns a new empty hash without arguments" do
ret = @hash.slice
ret.should_not equal(@hash)
ret.should be_an_instance_of(Hash)
ret.should == {}
end
it "returns the requested subset" do
@hash.slice(:c, :a).should == { c: 3, a: 1 }
end
it "returns a hash ordered in the order of the requested keys" do
@hash.slice(:c, :a).keys.should == [:c, :a]
end
it "returns only the keys of the original hash" do
@hash.slice(:a, :chunky_bacon).should == { a: 1 }
end
it "returns a Hash instance, even on subclasses" do
klass = Class.new(Hash)
h = klass.new
h[:bar] = 12
h[:foo] = 42
r = h.slice(:foo)
r.should == {foo: 42}
r.class.should == Hash
end
it "uses the regular Hash#[] method, even on subclasses that override it" do
ScratchPad.record []
klass = Class.new(Hash) do
def [](value)
ScratchPad << :used_subclassed_operator
super
end
end
h = klass.new
h[:bar] = 12
h[:foo] = 42
h.slice(:foo)
ScratchPad.recorded.should == []
end
it "does not retain the default value" do
h = Hash.new(1)
h.slice(:a).default.should be_nil
h[:a] = 1
h.slice(:a).default.should be_nil
end
it "does not retain the default_proc" do
pr = proc { |h, k| h[k] = [] }
h = Hash.new(&pr)
h.slice(:a).default_proc.should be_nil
h[:a] = 1
h.slice(:a).default_proc.should be_nil
end
it "retains compare_by_identity flag" do
h = { a: 9, c: 4 }.compare_by_identity
h2 = h.slice(:a)
h2.compare_by_identity?.should == true
end
end
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