Make a 'debug' command that replaces ./bin/console

This may as well be a part of the tool as it
could be useful to be able to jump into a
console for various reasons once the tool is
installed. It's not just useful during
development.

lib/zz.rb

@@ -4,6 +4,7 @@
 require "zz/help"
 require "zz/path"
 
+require "zz/commands/debug"
 require "zz/commands/provision"
 
 require "zz/base"

lib/zz/base.rb

@@ -1,5 +1,5 @@
 module ZZ
-  COMMANDS = [Provision]
+  COMMANDS = [Debug, Provision]
 
   def self.execute(args)
     command_name = args.shift

lib/zz/commands/debug.rb

@@ -0,0 +1,42 @@
+module ZZ
+  module Debug
+    class << self
+      def execute(args)
+        run_pry
+      rescue LoadError
+        run_irb
+      end
+
+      def run_pry
+        require "pry"
+        ZZ.pry
+      end
+
+      def run_irb
+        require "irb"
+        IRB.start
+      end
+
+      def name
+        "debug"
+      end
+
+      def summary
+        "runs an introspective debugger for zz"
+      end
+
+      def description
+        [
+          "This command starts a pry session in the context of the tuzz",
+          "automation tool and falls back to irb if pry is unavailable. It is",
+          "useful for debugging problems with the tool and for calling library",
+          "code in ways that weren't anticipated... or were they?",
+        ].join("\n  ")
+      end
+
+      def options
+        []
+      end
+    end
+  end
+end

spec/spec_helper.rb

@@ -1,4 +1,5 @@
 require "rspec"
+require "irb"
 require "pry"
 require "fileutils"
 require "zz"

spec/zz/commands/debug_spec.rb

@@ -0,0 +1,19 @@
+RSpec.describe ZZ::Debug do
+  it "provides useful information about itself" do
+    expect(subject.name).to eq("debug")
+    expect(subject.summary).to eq("runs an introspective debugger for zz")
+    expect(subject.description).to match(/starts a pry session/)
+  end
+
+  it "runs pry" do
+    expect(ZZ).to receive(:pry)
+    subject.execute([])
+  end
+
+  it "falls back to irb if pry is unavailable" do
+    allow(subject).to receive(:run_pry).and_raise(LoadError)
+
+    expect(IRB).to receive(:start)
+    subject.execute([])
+  end
+end