1 files changed, 72 insertions, 0 deletions
diff --git a/spec/lib/gitlab/usage/metrics/instrumentations/generic_metric_spec.rb b/spec/lib/gitlab/usage/metrics/instrumentations/generic_metric_spec.rb
new file mode 100644
index 00000000000..158be34d39c
--- /dev/null
+++ b/spec/lib/gitlab/usage/metrics/instrumentations/generic_metric_spec.rb
@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Usage::Metrics::Instrumentations::GenericMetric do
+  shared_examples 'custom fallback' do |custom_fallback|
+    subject do
+      Class.new(described_class) do
+        fallback(custom_fallback)
+        value { Gitlab::Database.main.version }
+      end.new(time_frame: 'none')
+    end
+
+    describe '#value' do
+      it 'gives the correct value' do
+        expect(subject.value).to eq(Gitlab::Database.main.version)
+      end
+
+      context 'when raising an exception' do
+        it 'return the custom fallback' do
+          expect(Gitlab::Database.main).to receive(:version).and_raise('Error')
+          expect(subject.value).to eq(custom_fallback)
+        end
+      end
+    end
+  end
+
+  context 'with default fallback' do
+    subject do
+      Class.new(described_class) do
+        value { Gitlab::Database.main.version }
+      end.new(time_frame: 'none')
+    end
+
+    describe '#value' do
+      it 'gives the correct value' do
+        expect(subject.value).to eq(Gitlab::Database.main.version )
+      end
+
+      context 'when raising an exception' do
+        it 'return the default fallback' do
+          expect(Gitlab::Database.main).to receive(:version).and_raise('Error')
+          expect(subject.value).to eq(described_class::FALLBACK)
+        end
+      end
+    end
+  end
+
+  context 'with custom fallback -2' do
+    it_behaves_like 'custom fallback', -2
+  end
+
+  context 'with custom fallback nil' do
+    it_behaves_like 'custom fallback', nil
+  end
+
+  context 'with custom fallback false' do
+    it_behaves_like 'custom fallback', false
+  end
+
+  context 'with custom fallback true' do
+    it_behaves_like 'custom fallback', true
+  end
+
+  context 'with custom fallback []' do
+    it_behaves_like 'custom fallback', []
+  end
+
+  context 'with custom fallback { major: -1 }' do
+    it_behaves_like 'custom fallback', { major: -1 }
+  end
+end