Update testing matrix

* Add Rails 6.1 which has been out a long while
* Remove Rails 5.2 which is nearing end of life
* Remove Ruby 2.4 which is past end of life
* Stop allowing failure on Rails master

When first adding 6.1 to the matrix, some of the tests failed with
aborted transactions. Inspecting the postgres log I was able to see that
Rails was trying to query a non-existent `schema_migrations` table. It
seems that in Rails 6.1, the `schema_migrations` table is created
differently from previous versions -- perhaps on demand when the
database is first accessed?

This is important because we wrap our tests that use the database in
DatabaseCleaner using the transaction strategy. When DB cleaner
rolls back the transaction at the end of the test, it was also rolling
back the creation of the `schema_migrations` table.

To get around this, I call `SchemaMigration.create_table` before every
DB-dependent test.

I've stopped allowing failure on Rails master because it hid this error
(which is only an issue in tests, really) from us for too long.
Additionally, I wanted to add Ruby 3 as part of this change, but there
were some build failures so I will handle that separately.

.github/workflows/ci.yml

@@ -13,16 +13,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: ["2.7","2.4"]
-        rails: ["5.2", "6.0", "master"]
-        exclude:
-          - ruby: "2.4"
-            rails: "6.0"
-          - ruby: "2.4"
-            rails: "master"
-        include:
-          - rails: "master"
-            continue-on-error: true
+        ruby: ["2.7"]
+        rails: ["6.0", "6.1", "master"]
+        continue-on-error: [false]
 
     runs-on: ubuntu-latest
 

Gemfile

@@ -3,7 +3,7 @@ source "https://rubygems.org"
 # Specify your gem's dependencies in scenic.gemspec
 gemspec
 
-rails_version = ENV.fetch("RAILS_VERSION", "6.0")
+rails_version = ENV.fetch("RAILS_VERSION", "6.1")
 
 if rails_version == "master"
   rails_constraint = { github: "rails/rails" }

spec/spec_helper.rb

@@ -11,6 +11,8 @@
   DatabaseCleaner.strategy = :transaction
 
   config.around(:each, db: true) do |example|
+    ActiveRecord::SchemaMigration.create_table
+
     DatabaseCleaner.start
     example.run
     DatabaseCleaner.clean