MONGOID-4667 Test Mongoid on rails 5.1

.evergreen/.evg.yml

@@ -590,10 +590,14 @@ axes:
         display_name: "Rails-master"
         variables:
            RAILS: "master"
-      - id: "60"
-        display_name: "Rails 6.0"
+      - id: "51"
+        display_name: "Rails 5.1"
         variables:
-           RAILS: "60"
+           RAILS: "51"
+      - id: "52"
+        display_name: "Rails 5.2"
+        variables:
+           RAILS: "52"
   - id: "i18n"
     display_name: I18n version
     values:
@@ -770,13 +774,25 @@ buildvariants:
     - rhel70-small
   tasks:
      - name: "test"
-- matrix_name: "rails-60"
+- matrix_name: "rails-51"
+  matrix_spec:
+    driver: "current"
+    ruby: "ruby-2.5"
+    mongodb-version: "4.2"
+    topology: "standalone"
+    rails: '51'
+  display_name: "${rails}, ${driver}, ${mongodb-version}"
+  run_on:
+    - rhel70-small
+  tasks:
+     - name: "test"
+- matrix_name: "rails-52"
   matrix_spec:
     driver: "current"
     ruby: "ruby-2.6"
     mongodb-version: "4.2"
     topology: "standalone"
-    rails: '60'
+    rails: '52'
   display_name: "${rails}, ${driver}, ${mongodb-version}"
   run_on:
     - rhel70-small

Gemfile

@@ -2,8 +2,8 @@ source 'https://rubygems.org'
 gemspec
 
 gem 'rake'
-gem 'actionpack', '~> 5.1'
-gem 'activemodel', '~> 5.1'
+gem 'actionpack'
+gem 'activemodel'
 
 # https://jira.mongodb.org/browse/MONGOID-4614
 if RUBY_VERSION < '2.3'

gemfiles/rails_60.gemfile → gemfiles/rails_51.gemfile

@@ -1,8 +1,8 @@
 source 'https://rubygems.org'
 
 gem 'rake'
-gem 'actionpack', '~> 6.0.0'
-gem 'activemodel', '~> 6.0.0'
+gem 'actionpack', '~> 5.1.0'
+gem 'activemodel', '~> 5.1.0'
 
 if RUBY_VERSION < '2.3'
   gem 'i18n', '~> 1.0', '< 1.5'

gemfiles/rails_52.gemfile

@@ -0,0 +1,37 @@
+source 'https://rubygems.org'
+
+gem 'rake'
+gem 'actionpack', '~> 5.2.0'
+gem 'activemodel', '~> 5.2.0'
+
+if RUBY_VERSION < '2.3'
+  gem 'i18n', '~> 1.0', '< 1.5'
+  gem 'nokogiri', '<1.10'
+else
+  gem 'i18n', '~> 1.0'
+end
+
+group :test do
+  gem 'rspec-retry'
+  gem 'benchmark-ips'
+  gem 'rspec', '~> 3.7'
+  gem 'rspec-expectations', '~> 3.7', '>= 3.8.4'
+  gem 'fuubar'
+  gem 'rfc'
+  platforms :mri do
+    gem 'timeout-interrupt'
+  end
+end
+
+group :development, :testing do
+  gem 'yard'
+  platforms :mri do
+    if RUBY_VERSION < '2.3'
+      gem 'byebug', '~> 10.0'
+    else
+      gem 'byebug'
+    end
+  end
+end
+
+gemspec path: '..'