diff --git a/cmd/brewcask-ci.rb b/cmd/brewcask-ci.rb
index 65b42dd787..837c6a3aa4 100755
--- a/cmd/brewcask-ci.rb
+++ b/cmd/brewcask-ci.rb
@@ -4,7 +4,7 @@ require "utils/github"
 require "utils/formatter"
 
 require_relative "lib/capture"
-require_relative "lib/diffable"
+require_relative "lib/check"
 require_relative "lib/travis"
 
 module Hbc
@@ -48,60 +48,12 @@ module Hbc
           was_installed = cask.installed?
           cask_dependencies = CaskDependencies.new(cask).reject(&:installed?)
 
-          checks = {
-            installed_apps: Diffable.new do
-              ["/Applications", File.expand_path("~/Applications")]
-                .flat_map { |dir| Dir["#{dir}/**/*.app"] }
-            end,
-            installed_kexts: Diffable.new do
-              system_command!("/usr/sbin/kextstat", args: ["-kl"], print_stderr: false)
-                .stdout
-                .lines
-                .map { |l| l.match(/^.{52}([^\s]+)/)[1] }
-                .grep_v(/^com\.apple\./)
-            end,
-            installed_launchjobs: Diffable.new do
-              format_launchjob = lambda { |file|
-                name = file.basename(".plist").to_s
-                label = Plist.parse_xml(File.read(file))["Label"]
-                (name == label) ? name : "#{name} (#{label})"
-              }
-
-              [
-                "~/Library/LaunchAgents",
-                "~/Library/LaunchDaemons",
-                "/Library/LaunchAgents",
-                "/Library/LaunchDaemons",
-              ].map { |p| Pathname(p).expand_path }
-                .select(&:directory?)
-                .flat_map(&:children)
-                .select { |child| child.extname == ".plist" }
-                .map(&format_launchjob)
-            end,
-            loaded_launchjobs: Diffable.new do
-              launchctl = lambda do |sudo|
-                system_command!("/bin/launchctl", args: ["list"], print_stderr: false, sudo: sudo)
-                  .stdout
-                  .lines.drop(1)
-              end
-
-              [false, true]
-                .flat_map(&launchctl)
-                .map { |l| l.split(/\s+/)[2] }
-                .grep_v(/^com\.apple\./)
-            end,
-            installed_pkgs: Diffable.new do
-              Pathname("/var/db/receipts")
-                .children
-                .grep(/\.plist$/)
-                .map(&:basename)
-            end,
-          }
+          check = Check.new
 
           overall_success &= step "brew cask install #{cask.token}", "install" do
             Installer.new(cask, force: true).uninstall if was_installed
 
-            checks.values.each(&:before)
+            check.before
 
             Installer.new(cask, verbose: true).install
           end
@@ -120,30 +72,11 @@ module Hbc
               end
             end
 
-            checks.each do |name, check|
-              check.after
-              next unless check.changed?
+            check.after
 
-              success = false
+            $stderr.puts check.message unless check.success?
 
-              message = case name
-              when :installed_pkgs
-                "Some packages were not uninstalled."
-              when :loaded_launchjobs
-                "Some launch jobs were not unloaded."
-              when :installed_launchjobs
-                "Some launch jobs were not uninstalled."
-              when :installed_kexts
-                "Some kernel extensions were not uninstalled."
-              when :installed_apps
-                "Some applications were not uninstalled."
-              end
-
-              $stderr.puts Formatter.error(message, label: "Error")
-              $stderr.puts check.diff_lines.join("\n")
-            end
-
-            success
+            success && check.success?
           end
         end
 
diff --git a/cmd/lib/check.rb b/cmd/lib/check.rb
new file mode 100644
index 0000000000..143414b84e
--- /dev/null
+++ b/cmd/lib/check.rb
@@ -0,0 +1,155 @@
+require "forwardable"
+
+class Check
+  CHECKS = {
+    installed_apps: -> {
+      ["/Applications", File.expand_path("~/Applications")]
+        .flat_map { |dir| Dir["#{dir}/**/*.app"] }
+    },
+    installed_kexts: -> {
+      system_command!("/usr/sbin/kextstat", args: ["-kl"], print_stderr: false)
+        .stdout
+        .lines
+        .map { |l| l.match(/^.{52}([^\s]+)/)[1] }
+        .grep_v(/^com\.apple\./)
+    },
+    installed_pkgs: -> {
+      Pathname("/var/db/receipts")
+        .children
+        .grep(/\.plist$/)
+        .map { |path| path.basename.to_s.sub(/\.plist$/, "") }
+    },
+    installed_launchjobs: -> {
+      format_launchjob = lambda { |file|
+        name = file.basename(".plist").to_s
+        label = Plist.parse_xml(File.read(file))["Label"]
+        (name == label) ? name : "#{name} (#{label})"
+      }
+
+      [
+        "~/Library/LaunchAgents",
+        "~/Library/LaunchDaemons",
+        "/Library/LaunchAgents",
+        "/Library/LaunchDaemons",
+      ].map { |p| Pathname(p).expand_path }
+        .select(&:directory?)
+        .flat_map(&:children)
+        .select { |child| child.extname == ".plist" }
+        .map(&format_launchjob)
+    },
+    loaded_launchjobs: -> {
+      launchctl = lambda do |sudo|
+        system_command!("/bin/launchctl", args: ["list"], print_stderr: false, sudo: sudo)
+          .stdout
+          .lines.drop(1)
+      end
+
+      [false, true]
+        .flat_map(&launchctl)
+        .map { |l| l.split(/\s+/)[2] }
+        .grep_v(/^com\.apple\./)
+    },
+  }
+
+  class Diff
+    attr_reader :removed, :added
+
+    def initialize(before, after)
+      @before = before.sort.uniq
+      @after = after.sort.uniq
+      @removed = @before - @after
+      @added = @after - @before
+    end
+
+    def changed?
+      removed.any? || added.any?
+    end
+  end
+
+  def before
+    @before = {}
+
+    CHECKS.each do |name, block|
+      @before[name] = block.call
+    end
+  end
+
+  def after
+    @after = {}
+
+    CHECKS.each do |name, block|
+      @after[name] = block.call
+    end
+  end
+
+  def diff
+    return @diff if defined?(@diff)
+
+    @diff = {}
+
+    CHECKS.keys.each do |name|
+      @diff[name] = Diff.new(@before[name], @after[name])
+    end
+
+    @diff
+  end
+  private :diff
+
+  def success?
+    diff.values.map(&:added).all?(&:none?)
+  end
+
+  def message
+    return if success?
+
+    lines = []
+
+    pkg_files = diff[:installed_pkgs]
+                 .added
+                 .flat_map { |id| Hbc::Pkg.new(id).pkgutil_bom_all.map(&:to_s) }
+
+    installed_apps = diff[:installed_apps].added - pkg_files
+
+    if installed_apps.any?
+      lines << Formatter.error("Some applications are still installed, add them to #{Formatter.identifier("uninstall delete:")}", label: "Error")
+      lines << installed_apps.join("\n")
+    end
+
+    if diff[:installed_kexts].added.any?
+      lines << Formatter.error("Some kernel extensions are still installed, add them to #{Formatter.identifier("uninstall kext:")}", label: "Error")
+      lines << diff[:installed_kexts].added.join("\n")
+    end
+
+    if diff[:installed_pkgs].added.any?
+      lines << Formatter.error("Some packages are still installed, add them to #{Formatter.identifier("uninstall pkgutil:")}", label: "Error")
+      lines << diff[:installed_pkgs].added.join("\n")
+    end
+
+    if diff[:installed_launchjobs].added.any?
+      lines << Formatter.error("Some launch jobs are still installed, add them to #{Formatter.identifier("uninstall launchctl:")}", label: "Error")
+      lines << diff[:installed_launchjobs].added.join("\n")
+    end
+
+    running_apps = diff[:loaded_launchjobs]
+                     .added
+                     .select { |id| id.match?(/\.\d+\Z/) }
+                     .map { |id| id.sub(/\.\d+\Z/, "") }
+
+    loaded_launchjobs = diff[:loaded_launchjobs]
+                         .added
+                         .reject { |id| id.match?(/\.\d+\Z/) }
+
+    if running_apps.any?
+      lines << Formatter.error("Some applications are still running, add them to #{Formatter.identifier("uninstall quit:")}", label: "Error")
+      lines << running_apps.join("\n")
+    end
+
+    if loaded_launchjobs.any?
+      lines << "\n" unless s.empty?
+      lines << Formatter.error("Some launch jobs were not unloaded, add them to #{Formatter.identifier("uninstall launchctl:")}", label: "Error")
+      lines << loaded_launchjobs.join("\n")
+    end
+
+    lines.join("\n")
+  end
+end
diff --git a/cmd/lib/diffable.rb b/cmd/lib/diffable.rb
deleted file mode 100644
index 66a082119a..0000000000
--- a/cmd/lib/diffable.rb
+++ /dev/null
@@ -1,51 +0,0 @@
-class Diffable
-  def initialize(&block)
-    @before = nil
-    @after = nil
-    @gather = block
-  end
-
-  def gather
-    @gather.call.sort.uniq
-  end
-
-  def before
-    @before ||= gather
-  end
-
-  def after
-    @after ||= gather
-  end
-
-  def diff
-    removed = before.reject { |e| after.include?(e) }
-    added = after - before
-
-    [removed, added]
-  end
-
-  def changed?
-    removed, added = diff
-    removed.any? || added.any?
-  end
-
-  def combined
-    (before + after).sort.uniq
-  end
-
-  def diff_lines(skip_unchanged: true)
-    removed, added = diff
-
-    lines = combined.flat_map do |e|
-      if removed.include?(e)
-        "#{Tty.red}- #{e}#{Tty.reset}"
-      elsif added.include?(e)
-        "#{Tty.green}+ #{e}#{Tty.reset}"
-      else
-        skip_unchanged ? [] : "  #{e}"
-      end
-    end
-
-    lines
-  end
-end