Run tests on Travis under JRuby

This required fixing the tests so that they could run on JRuby. JRuby
seems to not fully support `spawn`, in the sense that even if you
explicitly tell it to redirect stdout and stderr in the child process
using `out: writer, err: [:child, :out]`, it doesn't work: stdout from
the process leaks through. The `childprocess` gem, however, does work,
so we use that instead.

Author: mcmire

.travis.yml

@@ -1,3 +1,4 @@
 language: ruby
 rvm:
   - 2.5.1
+  - jruby-9.2.0.0

Gemfile

@@ -4,12 +4,13 @@ source "https://rubygems.org"
 
 git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
 
+gem "childprocess"
+gem "pry-nav", platform: :jruby
 gem "rake"
 gem "rubocop"
 gem "rspec-core", github: "rspec/rspec-core"
 gem "rspec-support", github: "rspec/rspec-support"
 gem "rspec-expectations", github: "rspec/rspec-expectations"
 gem "rspec-mocks", github: "rspec/rspec-mocks"
-gem "pry-byebug", platform: :mri
 
 gemspec

Gemfile.lock

@@ -38,23 +38,32 @@ GEM
   remote: https://rubygems.org/
   specs:
     ast (2.4.0)
-    byebug (10.0.2)
+    childprocess (0.9.0)
+      ffi (~> 1.0, >= 1.0.11)
     coderay (1.1.2)
     diff-lcs (1.3)
+    ffi (1.9.25)
+    ffi (1.9.25-java)
     jaro_winkler (1.5.1)
-    method_source (0.9.0)
+    jaro_winkler (1.5.1-java)
+    method_source (0.8.2)
     parallel (1.12.1)
     parser (2.5.1.2)
       ast (~> 2.4.0)
     patience_diff (1.1.0)
       trollop (~> 1.16)
     powerpack (0.1.2)
-    pry (0.11.3)
+    pry (0.10.4)
       coderay (~> 1.1.0)
-      method_source (~> 0.9.0)
-    pry-byebug (3.6.0)
-      byebug (~> 10.0)
-      pry (~> 0.10)
+      method_source (~> 0.8.1)
+      slop (~> 3.4)
+    pry (0.10.4-java)
+      coderay (~> 1.1.0)
+      method_source (~> 0.8.1)
+      slop (~> 3.4)
+      spoon (~> 0.0)
+    pry-nav (0.2.4)
+      pry (>= 0.9.10, < 0.11.0)
     rainbow (3.0.0)
     rake (12.3.1)
     rubocop (0.58.2)
@@ -66,14 +75,19 @@ GEM
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.0, >= 1.0.1)
     ruby-progressbar (1.10.0)
+    slop (3.6.0)
+    spoon (0.0.6)
+      ffi
     trollop (1.16.2)
     unicode-display_width (1.4.0)
 
 PLATFORMS
+  java
   ruby
 
 DEPENDENCIES
-  pry-byebug
+  childprocess
+  pry-nav
   rake
   rspec-core!
   rspec-expectations!
@@ -83,4 +97,4 @@ DEPENDENCIES
   super_diff!
 
 BUNDLED WITH
-   1.16.4
+   1.16.5

lib/super_diff.rb

@@ -1,6 +1,5 @@
 require "patience_diff"
 require "diff-lcs"
-require "pry-byebug"
 
 require_relative "super_diff/csi"
 require_relative "super_diff/errors"

spec/spec_helper.rb

@@ -1,6 +1,16 @@
 require_relative "../lib/super_diff"
 require_relative "../lib/super_diff/rspec"
 
+begin
+  require "pry-byebug"
+rescue LoadError
+end
+
+begin
+  require "pry-nav"
+rescue LoadError
+end
+
 Dir.glob(File.expand_path("../support/**/*.rb", __FILE__)).each do |file|
   require file
 end

spec/support/command_runner.rb

@@ -1,3 +1,5 @@
+require "childprocess"
+
 require "English"
 require "shellwords"
 require "timeout"
@@ -109,11 +111,14 @@ def initialize(*args)
     @args = args
     @options = options.merge(
       err: [:child, :out],
-      out: writer
+      out: @writer
     )
     @env = extract_env_from(@options)
 
-    @wrapper = ->(block) { block.call }
+    @process = ChildProcess.build(*command)
+    @process.io.stdout = @process.io.stderr = @writer
+
+    @wrapper = -> (block) { block.call }
     self.directory = Dir.pwd
     @run_quickly = false
     @run_successfully = false
@@ -203,7 +208,7 @@ def has_output?(expected_output)
 
   protected
 
-  attr_reader :args, :reader, :writer, :wrapper
+  attr_reader :args, :reader, :writer, :wrapper, :process
 
   private
 
@@ -222,9 +227,8 @@ def formatted_env
   end
 
   def run_freely
-    pid = spawn(env, *command, options)
-    Process.waitpid(pid)
-    @status = $CHILD_STATUS
+    process.start
+    process.wait
   end
 
   def run_with_wrapper