1 files changed, 11 insertions, 0 deletions
diff --git a/spec/ruby/core/complex/to_s_spec.rb b/spec/ruby/core/complex/to_s_spec.rb
index 989a7ae0b7..ceccffe470 100644
--- a/spec/ruby/core/complex/to_s_spec.rb
+++ b/spec/ruby/core/complex/to_s_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative '../numeric/fixtures/classes'
 
 describe "Complex#to_s" do
   describe "when self's real component is 0" do
@@ -41,4 +42,14 @@ describe "Complex#to_s" do
   it "returns 1+NaN*i for Complex(1, NaN)" do
     Complex(1, nan_value).to_s.should == "1+NaN*i"
   end
+
+  it "treats real and imaginary parts as strings" do
+    real = NumericSpecs::Subclass.new
+    # + because of https://bugs.ruby-lang.org/issues/20337
+    real.should_receive(:to_s).and_return(+"1")
+    imaginary = NumericSpecs::Subclass.new
+    imaginary.should_receive(:to_s).and_return("2")
+    imaginary.should_receive(:<).any_number_of_times.and_return(false)
+    Complex(real, imaginary).to_s.should == "1+2i"
+  end
 end