1 files changed, 14 insertions, 2 deletions
diff --git a/spec/ruby/core/env/shared/key.rb b/spec/ruby/core/env/shared/key.rb
index 43299beadb..fcb3a9b8c5 100644
--- a/spec/ruby/core/env/shared/key.rb
+++ b/spec/ruby/core/env/shared/key.rb
@@ -1,11 +1,23 @@
 describe :env_key, shared: true do
+  before :each do
+    @saved_foo = ENV["foo"]
+  end
+
+  after :each do
+    ENV["foo"] = @saved_foo
+  end
+
   it "returns the index associated with the passed value" do
     ENV["foo"] = "bar"
     ENV.send(@method, "bar").should == "foo"
-    ENV.delete "foo"
   end
 
   it "returns nil if the passed value is not found" do
-    ENV.send(@method, "should_never_be_set").should be_nil
+    ENV.delete("foo")
+    ENV.send(@method, "foo").should be_nil
+  end
+
+  it "raises TypeError if the argument is not a String and does not respond to #to_str" do
+    -> { ENV.send(@method, Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into String")
   end
 end