1 files changed, 63 insertions, 0 deletions
diff --git a/spec/lib/initializer_connections_spec.rb b/spec/lib/initializer_connections_spec.rb
new file mode 100644
index 00000000000..4ca283c4f22
--- /dev/null
+++ b/spec/lib/initializer_connections_spec.rb
@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe InitializerConnections do
+  describe '.with_disabled_database_connections', :reestablished_active_record_base do
+    def block_with_database_call
+      described_class.with_disabled_database_connections do
+        Project.first
+      end
+    end
+
+    def block_with_error
+      described_class.with_disabled_database_connections do
+        raise "oops, an error"
+      end
+    end
+
+    it 'prevents any database connection within the block' do
+      expect { block_with_database_call }.to raise_error(/Database connection should not be called during initializer/)
+    end
+
+    it 'does not prevent database connection if SKIP_RAISE_ON_INITIALIZE_CONNECTIONS is set' do
+      stub_env('SKIP_RAISE_ON_INITIALIZE_CONNECTIONS', '1')
+
+      expect { block_with_database_call }.not_to raise_error
+    end
+
+    it 'prevents any database connection if SKIP_RAISE_ON_INITIALIZE_CONNECTIONS is false' do
+      stub_env('SKIP_RAISE_ON_INITIALIZE_CONNECTIONS', 'false')
+
+      expect { block_with_database_call }.to raise_error(/Database connection should not be called during initializer/)
+    end
+
+    it 'restores original connection handler' do
+      # rubocop:disable Database/MultipleDatabases
+      original_handler = ActiveRecord::Base.connection_handler
+
+      expect { block_with_database_call }.to raise_error(/Database connection should not be called during initializer/)
+
+      expect(ActiveRecord::Base.connection_handler).to eq(original_handler)
+      # rubocop:enabled Database/MultipleDatabases
+    end
+
+    it 'restores original connection handler even there is an error' do
+      # rubocop:disable Database/MultipleDatabases
+      original_handler = ActiveRecord::Base.connection_handler
+
+      expect { block_with_error }.to raise_error(/an error/)
+
+      expect(ActiveRecord::Base.connection_handler).to eq(original_handler)
+      # rubocop:enabled Database/MultipleDatabases
+    end
+
+    it 'raises if any new connection_pools are established in the block' do
+      expect do
+        described_class.with_disabled_database_connections do
+          ApplicationRecord.connects_to database: { writing: :main, reading: :main }
+        end
+      end.to raise_error(/Unxpected connection_pools/)
+    end
+  end
+end