Add integration test

test/integration/background_stdin_test.rb

@@ -0,0 +1,57 @@
+require "test_helper"
+
+class BackgroundStdinTest < Minitest::Test
+  def test_background_stdin_write
+    Dir.mktmpdir do |dir|
+      Dir.chdir(dir) do
+        dir = Pathname(dir)
+        script = dir.join("script.rb")
+        script.write <<~'EOF'
+          $stdout.sync = true
+
+          print "> "
+          while line = gets
+            puts line
+            if line.strip == "exit"
+              puts "Bye"
+              return
+            else
+              puts "You said: #{line}"
+            end
+            print "> "
+          end
+        EOF
+
+        source_path = dir.join("RUNDOC.md")
+        source_path.write <<~EOF
+          ```
+          :::>- background.start("ruby #{script}",
+            name: "script",
+            wait: ">",
+            timeout: 15
+          )
+          :::-- background.stdin_write("hello", name: "script", wait: "hello")
+          :::-- background.stdin_write("exit", name: "script", wait: "exit")
+          :::>> background.stop(name: "script")
+          ```
+        EOF
+
+        io = StringIO.new
+        Rundoc::CLI.new(
+          io: io,
+          source_path: source_path,
+          on_success_dir: dir.join(SUCCESS_DIRNAME)
+        ).call
+
+        readme = dir.join(SUCCESS_DIRNAME).join("README.md").read
+        expected = <<~EOF
+          > hello
+          You said: hello
+          > exit
+          Bye
+        EOF
+        assert readme.include?(expected)
+      end
+    end
+  end
+end