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require_relative '../../spec_helper'
require_relative 'fixtures/classes'
describe "Hash#shift" do
it "removes a pair from hash and return it" do
h = { a: 1, b: 2, "c" => 3, nil => 4, [] => 5 }
h2 = h.dup
h.size.times do |i|
r = h.shift
r.should be_kind_of(Array)
h2[r.first].should == r.last
h.size.should == h2.size - i - 1
end
h.should == {}
end
# MRI explicitly implements this behavior
it "allows shifting entries while iterating" do
h = { a: 1, b: 2, c: 3 }
visited = []
shifted = []
h.each_pair { |k,v|
visited << k
shifted << h.shift
}
visited.should == [:a, :b, :c]
shifted.should == [[:a, 1], [:b, 2], [:c, 3]]
h.should == {}
end
it "calls #default with nil if the Hash is empty" do
h = {}
def h.default(key)
key.should == nil
:foo
end
h.shift.should == :foo
end
it "returns nil from an empty hash" do
{}.shift.should == nil
end
it "returns (computed) default for empty hashes" do
Hash.new(5).shift.should == 5
h = Hash.new { |*args| args }
h.shift.should == [h, nil]
end
it "preserves Hash invariants when removing the last item" do
h = { :a => 1, :b => 2 }
h.shift.should == [:a, 1]
h.shift.should == [:b, 2]
h[:c] = 3
h.should == {:c => 3}
end
it "raises a #{frozen_error_class} if called on a frozen instance" do
lambda { HashSpecs.frozen_hash.shift }.should raise_error(frozen_error_class)
lambda { HashSpecs.empty_frozen_hash.shift }.should raise_error(frozen_error_class)
end
it "works when the hash is at capacity" do
# We try a wide range of sizes in hopes that this will cover all implementationss base Hash size.
results = []
1.upto(100) do |n|
h = {}
n.times do |i|
h[i] = i
end
h.shift
results << h.size
end
results.should == 0.upto(99).to_a
end
end
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