Added more tests

lib/gitlab/usage/metrics/instrumentations/generic_metric.rb

@@ -15,22 +15,23 @@ module Gitlab
           FALLBACK = -1
 
           class << self
-            attr_reader :metric_operation
+            attr_reader :metric_operation, :metric_value
+
             @metric_operation = :alt
 
-            def fallback(custom_fallback)
+            def fallback(custom_fallback = FALLBACK)
+              return @metric_fallback if defined?(@metric_fallback)
+
               @metric_fallback = custom_fallback
             end
 
             def value(&block)
               @metric_value = block
             end
-
-            attr_reader :metric_value, :metric_fallback
           end
 
           def value
-            alt_usage_data(fallback: fallback) do
+            alt_usage_data(fallback: self.class.fallback) do
               self.class.metric_value.call
             end
           end
@@ -40,10 +41,6 @@ module Gitlab
               self.class.metric_operation
             )
           end
-
-          def fallback
-            self.class.metric_fallback || FALLBACK
-          end
         end
       end
     end

spec/lib/gitlab/usage/metrics/instrumentations/generic_metric_spec.rb

@@ -3,23 +3,23 @@
 require 'spec_helper'
 
 RSpec.describe Gitlab::Usage::Metrics::Instrumentations::GenericMetric do
-  context 'with custom fallback' do
+  shared_examples 'custom fallback' do |custom_fallback|
     subject do
       Class.new(described_class) do
-        fallback(-2)
+        fallback(custom_fallback)
         value { Gitlab::Database.version }
       end.new(time_frame: 'none')
     end
 
     describe '#value' do
       it 'gives the correct value' do
-        expect(subject.value).to eq(Gitlab::Database.version )
+        expect(subject.value).to eq(Gitlab::Database.version)
       end
 
       context 'when raising an exception' do
         it 'return the custom fallback' do
           expect(Gitlab::Database).to receive(:version).and_raise('Error')
-          expect(subject.value).to eq(-2)
+          expect(subject.value).to eq(custom_fallback)
         end
       end
     end
@@ -38,11 +38,35 @@ RSpec.describe Gitlab::Usage::Metrics::Instrumentations::GenericMetric do
       end
 
       context 'when raising an exception' do
-        it 'return the custom fallback' do
+        it 'return the default fallback' do
           expect(Gitlab::Database).to receive(:version).and_raise('Error')
-          expect(subject.value).to eq(-1)
+          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