1 files changed, 74 insertions, 0 deletions
diff --git a/spec/initializers/0_log_deprecations_spec.rb b/spec/initializers/0_log_deprecations_spec.rb
new file mode 100644
index 00000000000..35bceb2f132
--- /dev/null
+++ b/spec/initializers/0_log_deprecations_spec.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe '0_log_deprecations' do
+  def load_initializer
+    load Rails.root.join('config/initializers/0_log_deprecations.rb')
+  end
+
+  let(:env_var) { '1' }
+
+  before do
+    stub_env('GITLAB_LOG_DEPRECATIONS', env_var)
+    load_initializer
+  end
+
+  after do
+    # reset state changed by initializer
+    Warning.clear
+    ActiveSupport::Notifications.unsubscribe('deprecation.rails')
+  end
+
+  context 'for Ruby deprecations' do
+    context 'when catching deprecations through Kernel#warn' do
+      it 'also logs them to deprecation logger' do
+        expect(Gitlab::DeprecationJsonLogger).to receive(:info).with(
+          message: 'ABC gem is deprecated',
+          source: 'ruby'
+        )
+
+        expect { warn('ABC gem is deprecated') }.to output.to_stderr
+      end
+    end
+
+    context 'for other messages from Kernel#warn' do
+      it 'does not log them to deprecation logger' do
+        expect(Gitlab::DeprecationJsonLogger).not_to receive(:info)
+
+        expect { warn('Sure is hot today') }.to output.to_stderr
+      end
+    end
+
+    context 'when disabled via environment' do
+      let(:env_var) { '0' }
+
+      it 'does not log them to deprecation logger' do
+        expect(Gitlab::DeprecationJsonLogger).not_to receive(:info)
+
+        expect { warn('ABC gem is deprecated') }.to output.to_stderr
+      end
+    end
+  end
+
+  context 'for Rails deprecations' do
+    it 'logs them to deprecation logger' do
+      expect(Gitlab::DeprecationJsonLogger).to receive(:info).with(
+        message: match(/^DEPRECATION WARNING: ABC will be removed/),
+        source: 'rails'
+      )
+
+      expect { ActiveSupport::Deprecation.warn('ABC will be removed') }.to output.to_stderr
+    end
+
+    context 'when disabled via environment' do
+      let(:env_var) { '0' }
+
+      it 'does not log them to deprecation logger' do
+        expect(Gitlab::DeprecationJsonLogger).not_to receive(:info)
+
+        expect { ActiveSupport::Deprecation.warn('ABC will be removed') }.to output.to_stderr
+      end
+    end
+  end
+end