1 files changed, 15 insertions, 0 deletions
diff --git a/spec/ruby/library/set/shared/difference.rb b/spec/ruby/library/set/shared/difference.rb
new file mode 100644
index 0000000000..52807709c3
--- /dev/null
+++ b/spec/ruby/library/set/shared/difference.rb
@@ -0,0 +1,15 @@
+describe :set_difference, shared: true do
+  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.send(@method, Set[:a, :b]).should == Set[:c]
+    @set.send(@method, [:b, :c]).should == Set[:a]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    lambda { @set.send(@method, 1) }.should raise_error(ArgumentError)
+    lambda { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
+  end
+end