1 files changed, 114 insertions, 0 deletions
diff --git a/spec/ruby/core/hash/rehash_spec.rb b/spec/ruby/core/hash/rehash_spec.rb
new file mode 100644
index 0000000000..fcd5a037bd
--- /dev/null
+++ b/spec/ruby/core/hash/rehash_spec.rb
@@ -0,0 +1,114 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Hash#rehash" do
+  it "reorganizes the Hash by recomputing all key hash codes" do
+    k1 = Object.new
+    k2 = Object.new
+    def k1.hash; 0; end
+    def k2.hash; 1; end
+
+    h = {}
+    h[k1] = :v1
+    h[k2] = :v2
+
+    def k1.hash; 1; end
+
+    # The key should no longer be found as the #hash changed.
+    # Hash values 0 and 1 should not conflict, even with 1-bit stored hash.
+    h.key?(k1).should == false
+
+    h.keys.include?(k1).should == true
+
+    h.rehash.should.equal?(h)
+    h.key?(k1).should == true
+    h[k1].should == :v1
+  end
+
+  it "calls #hash for each key" do
+    k1 = mock('k1')
+    k2 = mock('k2')
+    v1 = mock('v1')
+    v2 = mock('v2')
+
+    v1.should_not_receive(:hash)
+    v2.should_not_receive(:hash)
+
+    h = { k1 => v1, k2 => v2 }
+
+    k1.should_receive(:hash).twice.and_return(0)
+    k2.should_receive(:hash).twice.and_return(0)
+
+    h.rehash
+    h[k1].should == v1
+    h[k2].should == v2
+  end
+
+  it "removes duplicate keys" do
+    a = [1,2]
+    b = [1]
+
+    h = {}
+    h[a] = true
+    h[b] = true
+    b << 2
+    h.size.should == 2
+    h.keys.should == [a, b]
+    h.rehash
+    h.size.should == 1
+    h.keys.should == [a]
+  end
+
+  it "removes duplicate keys for large hashes" do
+    a = [1,2]
+    b = [1]
+
+    h = {}
+    h[a] = true
+    h[b] = true
+    100.times { |n| h[n] = true }
+    b << 2
+    h.size.should == 102
+    h.keys.should.include? a
+    h.keys.should.include? b
+    h.rehash
+    h.size.should == 101
+    h.keys.should.include? a
+    h.keys.should_not.include? [1]
+  end
+
+  it "iterates keys in insertion order" do
+    key = Class.new do
+      attr_reader :name
+
+      def initialize(name)
+        @name = name
+      end
+
+      def hash
+        123
+      end
+    end
+
+    a, b, c, d = key.new('a'), key.new('b'), key.new('c'), key.new('d')
+    h = { a => 1, b => 2, c => 3, d => 4 }
+    h.size.should == 4
+
+    key.class_exec do
+      def eql?(other)
+        true
+      end
+    end
+
+    h.rehash
+    h.size.should == 1
+    k, v = h.first
+    k.name.should == 'a'
+    v.should == 4
+  end
+
+  it "raises a FrozenError if called on a frozen instance" do
+    -> { HashSpecs.frozen_hash.rehash  }.should.raise(FrozenError)
+    -> { HashSpecs.empty_frozen_hash.rehash }.should.raise(FrozenError)
+  end
+end