Open3.capture* only exist on 1.9+.

spec/regression/GH-2298_capture3_accepts_trailing_options_spec.rb

@@ -1,10 +1,12 @@
 require 'open3'
 
-describe "Open3.popen3" do
-  it "accepts and ignores empty trailing options hash" do
-    # capture3 is an easy way to test popen3 options behavior
-    result = Open3.capture3('echo')
+if RUBY_VERSION > '1.9'
+  describe "Open3.popen3" do
+    it "accepts and ignores empty trailing options hash" do
+      # capture3 is an easy way to test popen3 options behavior
+      result = Open3.capture3('echo')
 
-    expect(result[0]).to eq "\n"
+      expect(result[0]).to eq "\n"
+    end
   end
 end