Captures proc output instead of calling it

demo.rb

@@ -414,7 +414,8 @@ def initialize
       "Custom Messages" => ["custom failure message", "custom message with block"],
       "Complex Objects" => ["struct comparison", "custom class object comparison", "test with metadata", "custom object with many instance variables"],
       "Fuzzy Matchers" => ["a_string_matching", "a_hash_including", "a_collection_containing_exactly", "an_instance_of", "include with hash conditions"],
-      "Yield Matchers" => ["yield_control", "yield_with_args"]
+      "Yield Matchers" => ["yield_control", "yield_with_args"],
+      "Output Matchers" => ["output to stdout", "output to stderr"]
     }
 
     categories.each do |category, descriptions|

lib/rspec/enriched_json/expectation_helper_wrapper.rb

@@ -4,6 +4,7 @@
 require "oj"
 require "rspec/expectations"
 require "rspec/support/differ"
+require "stringio"
 
 module RSpec
   module EnrichedJson
@@ -46,7 +47,15 @@ def serialize_value(value)
           if value.is_a?(Regexp)
             return Oj.dump(value.inspect, mode: :compat)
           elsif value.is_a?(Proc)
-            return value.call
+            original_stdout = $stdout
+            $stdout = StringIO.new
+
+            value.call
+
+            output = $stdout.string
+            $stdout = original_stdout
+
+            return output
           end
 
           Oj.dump(value, OJ_OPTIONS)

lib/rspec/enriched_json/version.rb

@@ -2,6 +2,6 @@
 
 module RSpec
   module EnrichedJson
-    VERSION = "0.8.2"
+    VERSION = "0.8.3"
   end
 end

spec/oj_serialization_spec.rb

@@ -42,15 +42,6 @@
       expect(result).to eq("/http:\\/\\/example\\.com/")
     end
   end
-
-  describe "serialization of Proc objects" do
-    it "calls a simple Proc" do
-      helloworld = proc { "Hello, world!" }
-      result = serializer.serialize_value(helloworld)
-      expect(result).to eq("Hello, world!")
-    end
-  end
-
   describe "Fallback behavior for errors" do
     it "uses fallback format when Oj.dump fails" do
       # Create an object that we'll mock to fail

spec/stdout_matcher_spec.rb

@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+RSpec.describe "Stdout matcher value capture" do
+  let(:formatter) { RSpec::EnrichedJson::Formatters::EnrichedJsonFormatter.new(StringIO.new) }
+
+  # Use the same Oj options for loading that we use for dumping
+  let(:oj_load_options) do
+    {
+      mode: :object,
+      symbol_keys: true,
+      auto_define: false,
+      create_additions: false
+    }
+  end
+
+  it "captures actual when spec passes" do
+    test_file = "spec/support/stdout_passing_spec.rb"
+    File.write(test_file, <<~RUBY)
+      RSpec.describe "Test" do
+        it "checks output" do
+          expect { puts "Hello" }.to output("Hello\\n").to_stdout
+        end
+      end
+    RUBY
+
+    output = run_rspec(test_file)
+    json = Oj.load(output)
+    example = json["examples"].first
+
+    expect(example["details"]["expected"]).to eq("\"Hello\\n\"")
+    expect(example["details"]["actual"]).to eq("Hello\n")
+  ensure
+    File.delete(test_file) if File.exist?(test_file)
+  end
+
+  it "captures actual when spec fails" do
+    test_file = "spec/support/stdout_passing_spec.rb"
+    File.write(test_file, <<~RUBY)
+      RSpec.describe "Test" do
+        it "checks output" do
+          expect { puts "Hello" }.to output("Bye\\n").to_stdout
+        end
+      end
+    RUBY
+
+    output = run_rspec(test_file)
+    json = Oj.load(output)
+    example = json["examples"].first
+
+    expect(example["details"]["expected"]).to eq("\"Bye\\n\"")
+    expect(example["details"]["actual"]).to eq("\"Hello\\n\"")
+  ensure
+    File.delete(test_file) if File.exist?(test_file)
+  end
+
+  private
+
+  def run_rspec(test_file)
+    output = nil
+    Dir.mktmpdir do |dir|
+      output_file = File.join(dir, "output.json")
+      cmd = "bundle exec rspec #{test_file} --format RSpec::EnrichedJson::Formatters::EnrichedJsonFormatter --out #{output_file} 2>&1"
+      system(cmd, out: File::NULL)
+      output = File.read(output_file)
+    end
+    output
+  end
+end