1 files changed, 13 insertions, 2 deletions
diff --git a/spec/ruby/core/set/minus_spec.rb b/spec/ruby/core/set/minus_spec.rb
index 72f98f985e..8574708559 100644
--- a/spec/ruby/core/set/minus_spec.rb
+++ b/spec/ruby/core/set/minus_spec.rb
@@ -1,6 +1,17 @@
 require_relative '../../spec_helper'
-require_relative 'shared/difference'
 
 describe "Set#-" do
-  it_behaves_like :set_difference, :-
+  before :each do
+    @set = Set[:a, :b, :c]
+  end
+
+  it "returns a new Set containing self's elements excluding the elements in the passed Enumerable" do
+    (@set - Set[:a, :b]).should == Set[:c]
+    (@set - [:b, :c]).should == Set[:a]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { @set - 1 }.should.raise(ArgumentError)
+    -> { @set - Object.new }.should.raise(ArgumentError)
+  end
 end