diff --git a/test/test-pll-unlock.cpp b/test/test-pll-unlock.cpp
new file mode 100644
index 0000000..c09bf90
--- /dev/null
+++ b/test/test-pll-unlock.cpp
@@ -0,0 +1,149 @@
+#include <stdio.h>
+
+#include <analyzer/plugins/plugin.hpp>
+#include <hei_util.hpp>
+#include <util/pdbg.hpp>
+#include <util/trace.hpp>
+
+#include "gtest/gtest.h"
+
+using namespace analyzer;
+
+static const auto nodeId =
+    static_cast<libhei::NodeId_t>(libhei::hash<libhei::NodeId_t>("PLL_UNLOCK"));
+
+// Sub-test #1 - single PLL unlock attention on proc 1, clock 1
+TEST(PllUnlock, TestSet1)
+{
+    pdbg_targets_init(nullptr);
+
+    libhei::Chip chip1{util::pdbg::getTrgt("/proc1"), P10_20};
+
+    libhei::Signature sig11{chip1, nodeId, 0, 1, libhei::ATTN_TYPE_CHECKSTOP};
+
+    auto plugin = PluginMap::getSingleton().get(chip1.getType(), "pll_unlock");
+
+    libhei::IsolationData isoData{};
+    isoData.addSignature(sig11);
+    ServiceData sd{sig11, AnalysisType::SYSTEM_CHECKSTOP, isoData};
+
+    // Call the PLL unlock plugin.
+    plugin(1, chip1, sd);
+
+    nlohmann::json j{};
+    std::string s{};
+
+    // Callout list
+    j = sd.getCalloutList();
+    s = R"([
+    {
+        "Deconfigured": false,
+        "Guarded": false,
+        "LocationCode": "P0",
+        "Priority": "M"
+    },
+    {
+        "Deconfigured": false,
+        "Guarded": false,
+        "LocationCode": "/proc1",
+        "Priority": "M"
+    }
+])";
+    EXPECT_EQ(s, j.dump(4));
+
+    // Callout FFDC
+    j = sd.getCalloutFFDC();
+    s = R"([
+    {
+        "Callout Type": "Clock Callout",
+        "Clock Type": "OSC_REF_CLOCK_1",
+        "Priority": "medium"
+    },
+    {
+        "Callout Type": "Hardware Callout",
+        "Guard": false,
+        "Priority": "medium",
+        "Target": "/proc1"
+    }
+])";
+    EXPECT_EQ(s, j.dump(4));
+}
+
+// Sub-test #2 - PLL unlock attention on multiple procs and clocks. Isolating
+//               only to proc 1 clock 0 PLL unlock attentions.
+TEST(PllUnlock, TestSet2)
+{
+    pdbg_targets_init(nullptr);
+
+    libhei::Chip chip0{util::pdbg::getTrgt("/proc0"), P10_20};
+    libhei::Chip chip1{util::pdbg::getTrgt("/proc1"), P10_20};
+
+    // PLL unlock signatures for each clock per processor.
+    libhei::Signature sig00{chip0, nodeId, 0, 0, libhei::ATTN_TYPE_CHECKSTOP};
+    libhei::Signature sig01{chip0, nodeId, 0, 1, libhei::ATTN_TYPE_CHECKSTOP};
+    libhei::Signature sig10{chip1, nodeId, 0, 0, libhei::ATTN_TYPE_CHECKSTOP};
+    libhei::Signature sig11{chip1, nodeId, 0, 1, libhei::ATTN_TYPE_CHECKSTOP};
+
+    // Plugins for each processor.
+    auto plugin = PluginMap::getSingleton().get(chip1.getType(), "pll_unlock");
+
+    libhei::IsolationData isoData{};
+    isoData.addSignature(sig00);
+    isoData.addSignature(sig01);
+    isoData.addSignature(sig10);
+    isoData.addSignature(sig11);
+    ServiceData sd{sig10, AnalysisType::SYSTEM_CHECKSTOP, isoData};
+
+    // Call the PLL unlock plugin.
+    plugin(0, chip1, sd);
+
+    nlohmann::json j{};
+    std::string s{};
+
+    // Callout list
+    j = sd.getCalloutList();
+    s = R"([
+    {
+        "Deconfigured": false,
+        "Guarded": false,
+        "LocationCode": "P0",
+        "Priority": "H"
+    },
+    {
+        "Deconfigured": false,
+        "Guarded": false,
+        "LocationCode": "/proc0",
+        "Priority": "M"
+    },
+    {
+        "Deconfigured": false,
+        "Guarded": false,
+        "LocationCode": "/proc1",
+        "Priority": "M"
+    }
+])";
+    EXPECT_EQ(s, j.dump(4));
+
+    // Callout FFDC
+    j = sd.getCalloutFFDC();
+    s = R"([
+    {
+        "Callout Type": "Clock Callout",
+        "Clock Type": "OSC_REF_CLOCK_0",
+        "Priority": "high"
+    },
+    {
+        "Callout Type": "Hardware Callout",
+        "Guard": false,
+        "Priority": "medium",
+        "Target": "/proc0"
+    },
+    {
+        "Callout Type": "Hardware Callout",
+        "Guard": false,
+        "Priority": "medium",
+        "Target": "/proc1"
+    }
+])";
+    EXPECT_EQ(s, j.dump(4));
+}