Remove shared spec for hash_replace

This one was used in just one location, moving the specs inline.

core/hash/replace_spec.rb

@@ -1,7 +1,54 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
-require_relative 'shared/replace'
 
 describe "Hash#replace" do
-  it_behaves_like :hash_replace, :replace
+  it "replaces the contents of self with other" do
+    h = { a: 1, b: 2 }
+    h.replace(c: -1, d: -2).should equal(h)
+    h.should == { c: -1, d: -2 }
+  end
+
+  it "tries to convert the passed argument to a hash using #to_hash" do
+    obj = mock('{1=>2,3=>4}')
+    obj.should_receive(:to_hash).and_return({ 1 => 2, 3 => 4 })
+
+    h = {}
+    h.replace(obj)
+    h.should == { 1 => 2, 3 => 4 }
+  end
+
+  it "calls to_hash on hash subclasses" do
+    h = {}
+    h.replace(HashSpecs::ToHashHash[1 => 2])
+    h.should == { 1 => 2 }
+  end
+
+  it "does not transfer default values" do
+    hash_a = {}
+    hash_b = Hash.new(5)
+    hash_a.replace(hash_b)
+    hash_a.default.should == 5
+
+    hash_a = {}
+    hash_b = Hash.new { |h, k| k * 2 }
+    hash_a.replace(hash_b)
+    hash_a.default(5).should == 10
+
+    hash_a = Hash.new { |h, k| k * 5 }
+    hash_b = Hash.new(-> { raise "Should not invoke lambda" })
+    hash_a.replace(hash_b)
+    hash_a.default.should == hash_b.default
+  end
+
+  it "raises a FrozenError if called on a frozen instance that would not be modified" do
+    -> do
+      HashSpecs.frozen_hash.replace(HashSpecs.frozen_hash)
+    end.should raise_error(FrozenError)
+  end
+
+  it "raises a FrozenError if called on a frozen instance that is modified" do
+    -> do
+      HashSpecs.frozen_hash.replace(HashSpecs.empty_frozen_hash)
+    end.should raise_error(FrozenError)
+  end
 end