1 files changed, 60 insertions, 0 deletions
diff --git a/spec/lib/gitlab/memory/watchdog/monitor/heap_fragmentation_spec.rb b/spec/lib/gitlab/memory/watchdog/monitor/heap_fragmentation_spec.rb
new file mode 100644
index 00000000000..dad19cfd588
--- /dev/null
+++ b/spec/lib/gitlab/memory/watchdog/monitor/heap_fragmentation_spec.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+require 'support/shared_examples/lib/gitlab/memory/watchdog/monitor_result_shared_examples'
+require 'prometheus/client'
+
+RSpec.describe Gitlab::Memory::Watchdog::Monitor::HeapFragmentation do
+  let(:heap_frag_limit_gauge) { instance_double(::Prometheus::Client::Gauge) }
+  let(:max_heap_fragmentation) { 0.2 }
+  let(:fragmentation) { 0.3 }
+
+  subject(:monitor) do
+    described_class.new(max_heap_fragmentation: max_heap_fragmentation)
+  end
+
+  before do
+    allow(Gitlab::Metrics).to receive(:gauge)
+      .with(:gitlab_memwd_heap_frag_limit, anything)
+      .and_return(heap_frag_limit_gauge)
+    allow(heap_frag_limit_gauge).to receive(:set)
+
+    allow(Gitlab::Metrics::Memory).to receive(:gc_heap_fragmentation).and_return(fragmentation)
+  end
+
+  describe '#initialize' do
+    it 'sets the heap fragmentation limit gauge' do
+      expect(heap_frag_limit_gauge).to receive(:set).with({}, max_heap_fragmentation)
+
+      monitor
+    end
+  end
+
+  describe '#call' do
+    it 'gets gc_heap_fragmentation' do
+      expect(Gitlab::Metrics::Memory).to receive(:gc_heap_fragmentation)
+
+      monitor.call
+    end
+
+    context 'when process exceeds threshold' do
+      let(:fragmentation) { max_heap_fragmentation + 0.1 }
+      let(:payload) do
+        {
+          message: 'heap fragmentation limit exceeded',
+          memwd_cur_heap_frag: fragmentation,
+          memwd_max_heap_frag: max_heap_fragmentation
+        }
+      end
+
+      include_examples 'returns Watchdog Monitor result', threshold_violated: true
+    end
+
+    context 'when process does not exceed threshold' do
+      let(:fragmentation) { max_heap_fragmentation - 0.1 }
+      let(:payload) { {} }
+
+      include_examples 'returns Watchdog Monitor result', threshold_violated: false
+    end
+  end
+end