diff --git a/.gitignore b/.gitignore
index 50cae147..c507a689 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,4 @@ pkg
 Gemfile.lock
 coverage
 /.idea
+/gemfiles/*.gemfile.lock
diff --git a/.travis.base.yml b/.travis.base.yml
new file mode 100644
index 00000000..e0b96e26
--- /dev/null
+++ b/.travis.base.yml
@@ -0,0 +1,38 @@
+os: linux
+dist: xenial
+language: ruby
+cache: bundler
+script: "bundle exec rake test"
+rvm:
+  - 2.0
+  - 2.1
+  - 2.2
+  - 2.3
+  - 2.4
+  - 2.5
+  - 2.6
+  - 2.7
+  - 3.0
+  - head
+  - rbx
+gemfile:
+  - gemfiles/rails_3.0.gemfile
+  - gemfiles/rails_3.1.gemfile
+  - gemfiles/rails_3.2.gemfile
+  - gemfiles/rails_4.0.gemfile
+  - gemfiles/rails_4.1.gemfile
+  - gemfiles/rails_4.2.gemfile
+  - gemfiles/rails_5.0.gemfile
+  - gemfiles/rails_5.1.gemfile
+  - gemfiles/rails_5.2.gemfile
+  - gemfiles/rails_6.0.gemfile
+  - gemfiles/rails_6.1.gemfile
+  - gemfiles/rails_7_edge.gemfile
+  - gemfiles/datamapper.gemfile
+  - gemfiles/sequel.gemfile
+jobs:
+  allow_failures:
+    - rvm: head
+    - gemfile: gemfiles/rails_7_edge.gemfile
+    - rvm: rbx
+  fast_finish: true
diff --git a/.travis.yml b/.travis.yml
index f67ed619..ffcf417e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,109 +1,148 @@
-sudo: false
+---
+os: linux
+dist: xenial
 language: ruby
 cache: bundler
+script: bundle exec rake test
 rvm:
-  - 2.0
-  - 2.1
-  - 2.2
-  - 2.3
-  - 2.4
-  - 2.5
-  - 2.6
-  - 2.7
-  - 3.0
-  - rbx
-env:
-  - ACTIVERECORD=3.0.x
-  - ACTIVERECORD=3.1.x
-  - ACTIVERECORD=3.2.x
-  - ACTIVERECORD=4.0.x
-  - ACTIVERECORD=4.1.x
-  - ACTIVERECORD=4.2.x
-  - ACTIVERECORD=5.0.x
-  - ACTIVERECORD=5.1.x
-  - ACTIVERECORD=5.2.x
-  - ACTIVERECORD=6.0.x
-  - ACTIVERECORD=6.1.x
-  - ACTIVERECORD=6.2.x
-matrix:
-  exclude:
-    - rvm: 2.0
-      env: ACTIVERECORD=5.0.x
-    - rvm: 2.0
-      env: ACTIVERECORD=5.1.x
-    - rvm: 2.0
-      env: ACTIVERECORD=5.2.x
-    - rvm: 2.0
-      env: ACTIVERECORD=6.0.x
-    - rvm: 2.0
-      env: ACTIVERECORD=6.1.x
-    - rvm: 2.0
-      env: ACTIVERECORD=6.2.x
-    - rvm: 2.1
-      env: ACTIVERECORD=5.0.x
-    - rvm: 2.1
-      env: ACTIVERECORD=5.1.x
-    - rvm: 2.0
-      env: ACTIVERECORD=5.2.x
-    - rvm: 2.1
-      env: ACTIVERECORD=6.0.x
-    - rvm: 2.1
-      env: ACTIVERECORD=6.1.x
-    - rvm: 2.1
-      env: ACTIVERECORD=6.2.x
-    - rvm: 2.1
-      env: ACTIVERECORD=6.0.x
-    - rvm: 2.2
-      env: ACTIVERECORD=6.1.x
-    - rvm: 2.2
-      env: ACTIVERECORD=6.2.x
-    - rvm: 2.2
-      env: ACTIVERECORD=6.0.x
-    - rvm: 2.3
-      env: ACTIVERECORD=6.1.x
-    - rvm: 2.3
-      env: ACTIVERECORD=6.2.x
-    - rvm: 2.3
-      env: ACTIVERECORD=3.0.x
-    - rvm: 2.4
-      env: ACTIVERECORD=3.1.x
-    - rvm: 2.4
-      env: ACTIVERECORD=3.2.x
-    - rvm: 2.4
-      env: ACTIVERECORD=4.0.x
-    - rvm: 2.4
-      env: ACTIVERECORD=4.1.x
-    - rvm: 2.4
-      env: ACTIVERECORD=6.0.x
-    - rvm: 2.4
-      env: ACTIVERECORD=6.1.x
-    - rvm: 2.4
-      env: ACTIVERECORD=6.2.x
-    - rvm: 2.5
-      env: ACTIVERECORD=3.0.x
-    - rvm: 2.5
-      env: ACTIVERECORD=3.1.x
-    - rvm: 2.5
-      env: ACTIVERECORD=3.2.x
-    - rvm: 2.5
-      env: ACTIVERECORD=4.0.x
-    - rvm: 2.5
-      env: ACTIVERECORD=4.1.x
-    - rvm: rbx
-      env: ACTIVERECORD=5.0.x
-    - rvm: rbx
-      env: ACTIVERECORD=5.1.x
-    - rvm: rbx
-      env: ACTIVERECORD=5.2.x
-    - rvm: rbx
-      env: ACTIVERECORD=6.0.x
-    - rvm: rbx
-      env: ACTIVERECORD=6.1.x
-    - rvm: rbx
-      env: ACTIVERECORD=6.2.x
+- 2.0
+- 2.1
+- 2.2
+- 2.3
+- 2.4
+- 2.5
+- 2.6
+- 2.7
+- 3.0
+- head
+- rbx
+gemfile:
+- gemfiles/rails_3.0.gemfile
+- gemfiles/rails_3.1.gemfile
+- gemfiles/rails_3.2.gemfile
+- gemfiles/rails_4.0.gemfile
+- gemfiles/rails_4.1.gemfile
+- gemfiles/rails_4.2.gemfile
+- gemfiles/rails_5.0.gemfile
+- gemfiles/rails_5.1.gemfile
+- gemfiles/rails_5.2.gemfile
+- gemfiles/rails_6.0.gemfile
+- gemfiles/rails_6.1.gemfile
+- gemfiles/rails_7_edge.gemfile
+- gemfiles/datamapper.gemfile
+- gemfiles/sequel.gemfile
+jobs:
   allow_failures:
-    - rvm: rbx
+  - rvm: head
+  - gemfile: gemfiles/rails_7_edge.gemfile
+  - rvm: rbx
+  - gemfile: gemfiles/rails_4.2.gemfile
+    rvm: '2.0'
+  - gemfile: gemfiles/rails_4.2.gemfile
+    rvm: '2.1'
+  - gemfile: gemfiles/rails_4.2.gemfile
+    rvm: '2.2'
+  - gemfile: gemfiles/rails_4.2.gemfile
+    rvm: '2.3'
+  - gemfile: gemfiles/rails_4.2.gemfile
+    rvm: '2.4'
   fast_finish: true
-addons:
-  code_climate:
-    repo_token: a90435ed4954dd6e9f3697a20c5bc3754f67d94703f870e8fc7b00f69f5b2d06
+  exclude:
+  - gemfile: gemfiles/rails_3.0.gemfile
+    rvm: '2.4'
+  - gemfile: gemfiles/rails_3.0.gemfile
+    rvm: '2.5'
+  - gemfile: gemfiles/rails_3.0.gemfile
+    rvm: '2.6'
+  - gemfile: gemfiles/rails_3.0.gemfile
+    rvm: '2.7'
+  - gemfile: gemfiles/rails_3.0.gemfile
+    rvm: '3.0'
+  - gemfile: gemfiles/rails_3.1.gemfile
+    rvm: '2.4'
+  - gemfile: gemfiles/rails_3.1.gemfile
+    rvm: '2.5'
+  - gemfile: gemfiles/rails_3.1.gemfile
+    rvm: '2.6'
+  - gemfile: gemfiles/rails_3.1.gemfile
+    rvm: '2.7'
+  - gemfile: gemfiles/rails_3.1.gemfile
+    rvm: '3.0'
+  - gemfile: gemfiles/rails_3.2.gemfile
+    rvm: '2.4'
+  - gemfile: gemfiles/rails_3.2.gemfile
+    rvm: '2.5'
+  - gemfile: gemfiles/rails_3.2.gemfile
+    rvm: '2.6'
+  - gemfile: gemfiles/rails_3.2.gemfile
+    rvm: '2.7'
+  - gemfile: gemfiles/rails_3.2.gemfile
+    rvm: '3.0'
+  - gemfile: gemfiles/rails_4.0.gemfile
+    rvm: '2.4'
+  - gemfile: gemfiles/rails_4.0.gemfile
+    rvm: '2.5'
+  - gemfile: gemfiles/rails_4.0.gemfile
+    rvm: '2.6'
+  - gemfile: gemfiles/rails_4.0.gemfile
+    rvm: '2.7'
+  - gemfile: gemfiles/rails_4.0.gemfile
+    rvm: '3.0'
+  - gemfile: gemfiles/rails_4.1.gemfile
+    rvm: '2.4'
+  - gemfile: gemfiles/rails_4.1.gemfile
+    rvm: '2.5'
+  - gemfile: gemfiles/rails_4.1.gemfile
+    rvm: '2.6'
+  - gemfile: gemfiles/rails_4.1.gemfile
+    rvm: '2.7'
+  - gemfile: gemfiles/rails_4.1.gemfile
+    rvm: '3.0'
+  - gemfile: gemfiles/rails_5.0.gemfile
+    rvm: '2.0'
+  - gemfile: gemfiles/rails_5.0.gemfile
+    rvm: '2.1'
+  - gemfile: gemfiles/rails_5.1.gemfile
+    rvm: '2.0'
+  - gemfile: gemfiles/rails_5.1.gemfile
+    rvm: '2.1'
+  - gemfile: gemfiles/rails_5.2.gemfile
+    rvm: '2.0'
+  - gemfile: gemfiles/rails_5.2.gemfile
+    rvm: '2.1'
+  - gemfile: gemfiles/rails_5.2.gemfile
+    rvm: '2.2'
+  - gemfile: gemfiles/rails_5.2.gemfile
+    rvm: '2.3'
+  - gemfile: gemfiles/rails_5.2.gemfile
+    rvm: '2.4'
+  - gemfile: gemfiles/rails_6.0.gemfile
+    rvm: '2.0'
+  - gemfile: gemfiles/rails_6.0.gemfile
+    rvm: '2.1'
+  - gemfile: gemfiles/rails_6.0.gemfile
+    rvm: '2.2'
+  - gemfile: gemfiles/rails_6.0.gemfile
+    rvm: '2.3'
+  - gemfile: gemfiles/rails_6.0.gemfile
+    rvm: '2.4'
+  - gemfile: gemfiles/rails_6.1.gemfile
+    rvm: '2.0'
+  - gemfile: gemfiles/rails_6.1.gemfile
+    rvm: '2.1'
+  - gemfile: gemfiles/rails_6.1.gemfile
+    rvm: '2.2'
+  - gemfile: gemfiles/rails_6.1.gemfile
+    rvm: '2.3'
+  - gemfile: gemfiles/rails_6.1.gemfile
+    rvm: '2.4'
+  - gemfile: gemfiles/rails_7_edge.gemfile
+    rvm: '2.0'
+  - gemfile: gemfiles/rails_7_edge.gemfile
+    rvm: '2.1'
+  - gemfile: gemfiles/rails_7_edge.gemfile
+    rvm: '2.2'
+  - gemfile: gemfiles/rails_7_edge.gemfile
+    rvm: '2.3'
+  - gemfile: gemfiles/rails_7_edge.gemfile
+    rvm: '2.4'
diff --git a/Appraisals b/Appraisals
new file mode 100644
index 00000000..8e988636
--- /dev/null
+++ b/Appraisals
@@ -0,0 +1,31 @@
+
+SUPPORTED_RAILS_VERSIONS = %w[3.0 3.1 3.2 4.0 4.1 4.2 5.0 5.1 5.2 6.0 6.1]
+
+SUPPORTED_RAILS_VERSIONS.each do |rails_ver|
+  appraise "rails-#{rails_ver}" do
+    gem 'activerecord', "~> #{rails_ver}.x"
+    gem 'actionpack', "~> #{rails_ver}.x"
+
+    install_if -> { %w[3.0 3.1 3.2].include?(rails_ver) } do
+      gem 'activerecord-sqlite3-adapter'
+    end
+
+  end
+end
+
+appraise 'rails-7-edge' do
+  gem 'activerecord', git: 'https://github.com/rails/rails', branch: 'main'
+  gem 'actionpack', git: 'https://github.com/rails/rails', branch: 'main'
+end
+
+appraise 'datamapper' do
+  gem 'datamapper'
+  gem 'dm-sqlite-adapter'
+end
+
+appraise 'sequel' do
+  gem 'sequel'
+end
+
+
+
diff --git a/Gemfile b/Gemfile
index fa75df15..eafb552d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,29 @@
 source 'https://rubygems.org'
 
 gemspec
+
+gem 'appraisal'
+gem 'sqlite3'
+gem 'encryptor', '~> 3.0.0'
+gem 'rake'
+
+gem 'minitest'
+gem 'simplecov'
+gem 'simplecov-rcov'
+gem 'codeclimate-test-reporter', '<= 0.6.0'
+
+
+if RUBY_VERSION < '2.1.0'
+  gem 'nokogiri'
+  gem 'public_suffix', '< 3.0.0'
+end
+
+platforms :jruby do
+  gem 'activerecord-jdbcsqlite3-adapter'
+  gem 'jdbc-sqlite3', '< 3.8.7' # 3.8.7 is nice and broke
+end
+
+group :development do
+  gem 'wwtd',    require: false
+  gem 'rubocop', require: false
+end
diff --git a/Rakefile b/Rakefile
index 3dbc96ce..7f453bb0 100644
--- a/Rakefile
+++ b/Rakefile
@@ -3,6 +3,7 @@
 require 'rake/testtask'
 require 'rdoc/task'
 require "bundler/gem_tasks"
+require 'wwtd/tasks'
 
 desc 'Test the attr_encrypted gem.'
 Rake::TestTask.new(:test) do |t|
@@ -22,4 +23,7 @@ Rake::RDocTask.new(:rdoc) do |rdoc|
 end
 
 desc 'Default: run unit tests.'
-task :default => :test
+if !ENV["APPRAISAL_INITIALIZED"] && !ENV["TRAVIS"]
+  task :default => :appraisal
+end
+#task :default => :test
diff --git a/attr_encrypted.gemspec b/attr_encrypted.gemspec
index 8ee98af6..a640be4c 100644
--- a/attr_encrypted.gemspec
+++ b/attr_encrypted.gemspec
@@ -36,6 +36,7 @@ Gem::Specification.new do |s|
   s.required_ruby_version = '>= 2.0.0'
 
   s.add_dependency               'encryptor',    '~> 3.0.0'
+  s.add_development_dependency   'appraisal'
   s.add_development_dependency   'activerecord', '>= 2.0.0'
   s.add_development_dependency   'actionpack',   '>= 2.0.0'
   s.add_development_dependency   'datamapper'
diff --git a/gemfiles/datamapper.gemfile b/gemfiles/datamapper.gemfile
new file mode 100644
index 00000000..3d48f150
--- /dev/null
+++ b/gemfiles/datamapper.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "datamapper"
+gem "dm-sqlite-adapter"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_3.0.gemfile b/gemfiles/rails_3.0.gemfile
new file mode 100644
index 00000000..25b339e0
--- /dev/null
+++ b/gemfiles/rails_3.0.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 3.0.x"
+gem "actionpack", "~> 3.0.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_3.1.gemfile b/gemfiles/rails_3.1.gemfile
new file mode 100644
index 00000000..d501743e
--- /dev/null
+++ b/gemfiles/rails_3.1.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 3.1.x"
+gem "actionpack", "~> 3.1.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_3.2.gemfile b/gemfiles/rails_3.2.gemfile
new file mode 100644
index 00000000..5e4cd8ad
--- /dev/null
+++ b/gemfiles/rails_3.2.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 3.2.x"
+gem "actionpack", "~> 3.2.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_4.0.gemfile b/gemfiles/rails_4.0.gemfile
new file mode 100644
index 00000000..1a3ea043
--- /dev/null
+++ b/gemfiles/rails_4.0.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 4.0.x"
+gem "actionpack", "~> 4.0.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_4.1.gemfile b/gemfiles/rails_4.1.gemfile
new file mode 100644
index 00000000..c76f7e9b
--- /dev/null
+++ b/gemfiles/rails_4.1.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 4.1.x"
+gem "actionpack", "~> 4.1.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_4.2.gemfile b/gemfiles/rails_4.2.gemfile
new file mode 100644
index 00000000..94ebdf22
--- /dev/null
+++ b/gemfiles/rails_4.2.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 4.2.x"
+gem "actionpack", "~> 4.2.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_5.0.gemfile b/gemfiles/rails_5.0.gemfile
new file mode 100644
index 00000000..0e6fa56c
--- /dev/null
+++ b/gemfiles/rails_5.0.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 5.0.x"
+gem "actionpack", "~> 5.0.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_5.1.gemfile b/gemfiles/rails_5.1.gemfile
new file mode 100644
index 00000000..e51f0290
--- /dev/null
+++ b/gemfiles/rails_5.1.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 5.1.x"
+gem "actionpack", "~> 5.1.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_5.2.gemfile b/gemfiles/rails_5.2.gemfile
new file mode 100644
index 00000000..79dcf6a9
--- /dev/null
+++ b/gemfiles/rails_5.2.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 5.2.x"
+gem "actionpack", "~> 5.2.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_6.0.gemfile b/gemfiles/rails_6.0.gemfile
new file mode 100644
index 00000000..c4357c87
--- /dev/null
+++ b/gemfiles/rails_6.0.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 6.0.x"
+gem "actionpack", "~> 6.0.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_6.1.gemfile b/gemfiles/rails_6.1.gemfile
new file mode 100644
index 00000000..ecbc9384
--- /dev/null
+++ b/gemfiles/rails_6.1.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 6.1.x"
+gem "actionpack", "~> 6.1.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_6.2.gemfile b/gemfiles/rails_6.2.gemfile
new file mode 100644
index 00000000..c5f9fd75
--- /dev/null
+++ b/gemfiles/rails_6.2.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", "~> 6.2.x"
+gem "actionpack", "~> 6.2.x"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/rails_7_edge.gemfile b/gemfiles/rails_7_edge.gemfile
new file mode 100644
index 00000000..3ec7b50c
--- /dev/null
+++ b/gemfiles/rails_7_edge.gemfile
@@ -0,0 +1,13 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "activerecord", git: "https://github.com/rails/rails", branch: "main"
+gem "actionpack", git: "https://github.com/rails/rails", branch: "main"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/gemfiles/sequel.gemfile b/gemfiles/sequel.gemfile
new file mode 100644
index 00000000..3f4a7396
--- /dev/null
+++ b/gemfiles/sequel.gemfile
@@ -0,0 +1,12 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "sequel"
+
+group :development do
+  gem "wwtd", require: false
+  gem "rubocop", require: false
+end
+
+gemspec path: "../"
diff --git a/scripts/generate_travis_excludes.rb b/scripts/generate_travis_excludes.rb
new file mode 100755
index 00000000..7468c349
--- /dev/null
+++ b/scripts/generate_travis_excludes.rb
@@ -0,0 +1,76 @@
+#!/usr/bin/env ruby
+
+require 'rubygems'
+require 'yaml'
+
+class String
+  def versionish?
+    ::Gem::Version.correct?(self)
+  end
+end
+
+class Numeric
+  def versionish?
+    true
+  end
+end
+
+TRAVIS_TEMPLATE_PATH = File.expand_path('../.travis.base.yml', __dir__)
+TRAVIS_CONFIG_PATH = File.expand_path('../.travis.yml', __dir__)
+
+GEMFILE_RUBY_VERSIONS = {
+  'gemfiles/rails_3.0.gemfile':    '< 2.4',
+  'gemfiles/rails_3.1.gemfile':    '< 2.4',
+  'gemfiles/rails_3.2.gemfile':    '< 2.4',
+  'gemfiles/rails_4.0.gemfile':    '< 2.4',
+  'gemfiles/rails_4.1.gemfile':    '< 2.4',
+  # apparently supports up to at least ruby 2.5
+  'gemfiles/rails_4.2.gemfile':    '>= 0',
+  'gemfiles/rails_5.0.gemfile':    '>= 2.2',
+  'gemfiles/rails_5.1.gemfile':    '>= 2.2',
+  'gemfiles/rails_5.2.gemfile':    '>= 2.5',
+  'gemfiles/rails_6.0.gemfile':    '>= 2.5',
+  'gemfiles/rails_6.1.gemfile':    '>= 2.5',
+  'gemfiles/rails_7_edge.gemfile': '>= 2.5',
+  #'gemfiles/datamapper.gemfile':   '>= 0',
+  #'gemfiles/sequel.gemfile':       '>= 0',
+}.transform_values { |ver| Gem::Requirement.create(ver.to_s) }
+
+GEMFILE_FAILABLE_RUBY_VERSIONS = {
+  'gemfiles/rails_4.2.gemfile':   '>= 2.5',
+}.transform_values { |ver| Gem::Requirement.create(ver.to_s) }
+
+travis_config = YAML.load_file(TRAVIS_TEMPLATE_PATH)
+
+ruby_versions = travis_config['rvm'].select(&:versionish?).map { |ver| Gem::Version.new(ver) }
+
+travis_config['jobs'] ||= {}
+excludes  = (travis_config['jobs']['exclude'] ||= [])
+failables = (travis_config['jobs']['allow_failures'] ||= [])
+
+requirement_combinations = GEMFILE_RUBY_VERSIONS.to_a.product(ruby_versions)
+failable_combinations    = GEMFILE_FAILABLE_RUBY_VERSIONS.to_a.product(ruby_versions)
+
+requirement_combinations.each do |((gemfile, constraint), ruby_ver)|
+  next if constraint.satisfied_by?(ruby_ver)
+
+  excludes << {
+    'gemfile' => gemfile.to_s,
+    'rvm'     => ruby_ver.to_s
+  }
+end
+
+failable_combinations.each do |((gemfile, constraint), ruby_ver)|
+  next if constraint.satisfied_by?(ruby_ver)
+
+  failables << {
+    'gemfile' => gemfile.to_s,
+    'rvm'     => ruby_ver.to_s
+  }
+end
+
+File.open TRAVIS_CONFIG_PATH, 'wt' do |f|
+  YAML.dump(travis_config, f)
+end
+
+printf "Done. (%d excludes and %d allowed failures)\n", excludes.size, failables.size