diff --git a/test/openpower-pels/registry_test.cpp b/test/openpower-pels/registry_test.cpp
new file mode 100644
index 0000000..2107725
--- /dev/null
+++ b/test/openpower-pels/registry_test.cpp
@@ -0,0 +1,166 @@
+#include "extensions/openpower-pels/registry.hpp"
+
+#include <filesystem>
+#include <fstream>
+#include <nlohmann/json.hpp>
+
+#include <gtest/gtest.h>
+
+using namespace openpower::pels::message;
+namespace fs = std::filesystem;
+
+const auto registryData = R"(
+{
+    "PELs":
+    [
+        {
+            "Name": "xyz.openbmc_project.Power.Fault",
+            "Subsystem": "power_supply",
+            "ActionFlags": ["service_action", "report"],
+
+            "SRC":
+            {
+                "ReasonCode": "0x2030"
+            }
+        },
+
+        {
+            "Name": "xyz.openbmc_project.Power.OverVoltage",
+            "Subsystem": "power_control_hw",
+            "Severity": "unrecoverable",
+            "MfgSeverity": "non_error",
+            "ActionFlags": ["service_action", "report", "call_home"],
+            "MfgActionFlags": ["hidden"],
+
+            "SRC":
+            {
+                "ReasonCode": "0x2333",
+                "Type": "BD",
+                "SymptomIDFields": ["SRCWord5", "SRCWord6", "SRCWord7"],
+                "PowerFault": true,
+                "Words6To9":
+                {
+                    "6":
+                    {
+                        "description": "Failing unit number",
+                        "AdditionalDataPropSource": "PS_NUM"
+                    },
+
+                    "7":
+                    {
+                        "description": "bad voltage",
+                        "AdditionalDataPropSource": "VOLTAGE"
+                    }
+                }
+            }
+        }
+    ]
+}
+)";
+
+class RegistryTest : public ::testing::Test
+{
+  protected:
+    static void SetUpTestCase()
+    {
+        char path[] = "/tmp/regtestXXXXXX";
+        regDir = mkdtemp(path);
+    }
+
+    static void TearDownTestCase()
+    {
+        fs::remove_all(regDir);
+    }
+
+    static std::string writeData(const char* data)
+    {
+        fs::path path = regDir / "registry.json";
+        std::ofstream stream{path};
+        stream << data;
+        return path;
+    }
+
+    static fs::path regDir;
+};
+
+fs::path RegistryTest::regDir{};
+
+TEST_F(RegistryTest, TestNoEntry)
+{
+    auto path = RegistryTest::writeData(registryData);
+    Registry registry{path};
+
+    auto entry = registry.lookup("foo");
+    EXPECT_FALSE(entry);
+}
+
+TEST_F(RegistryTest, TestFindEntry)
+{
+    auto path = RegistryTest::writeData(registryData);
+    Registry registry{path};
+
+    auto entry = registry.lookup("xyz.openbmc_project.Power.OverVoltage");
+    ASSERT_TRUE(entry);
+    EXPECT_EQ(entry->name, "xyz.openbmc_project.Power.OverVoltage");
+    EXPECT_EQ(entry->subsystem, 0x62);
+    EXPECT_EQ(*(entry->severity), 0x40);
+    EXPECT_EQ(*(entry->mfgSeverity), 0x00);
+    EXPECT_EQ(entry->actionFlags, 0xA800);
+    EXPECT_EQ(*(entry->mfgActionFlags), 0x4000);
+    EXPECT_FALSE(entry->eventType);
+    EXPECT_FALSE(entry->eventScope);
+
+    // TODO: compare SRC fields
+}
+
+// Check the entry that mostly uses defaults
+TEST_F(RegistryTest, TestFindEntryMinimal)
+{
+    auto path = RegistryTest::writeData(registryData);
+    Registry registry{path};
+
+    auto entry = registry.lookup("xyz.openbmc_project.Power.Fault");
+    ASSERT_TRUE(entry);
+    EXPECT_EQ(entry->name, "xyz.openbmc_project.Power.Fault");
+    EXPECT_EQ(entry->subsystem, 0x61);
+    EXPECT_FALSE(entry->severity);
+    EXPECT_FALSE(entry->mfgSeverity);
+    EXPECT_FALSE(entry->mfgActionFlags);
+    EXPECT_EQ(entry->actionFlags, 0xA000);
+    EXPECT_FALSE(entry->eventType);
+    EXPECT_FALSE(entry->eventScope);
+}
+
+TEST_F(RegistryTest, TestBadJSON)
+{
+    auto path = RegistryTest::writeData("bad {} json");
+
+    Registry registry{path};
+
+    EXPECT_FALSE(registry.lookup("foo"));
+}
+
+// Test the helper functions the use the pel_values data.
+TEST_F(RegistryTest, TestHelperFunctions)
+{
+    using namespace openpower::pels::message::helper;
+    EXPECT_EQ(getSubsystem("input_power_source"), 0xA1);
+    EXPECT_THROW(getSubsystem("foo"), std::runtime_error);
+
+    EXPECT_EQ(getSeverity("symptom_recovered"), 0x71);
+    EXPECT_THROW(getSeverity("foo"), std::runtime_error);
+
+    EXPECT_EQ(getEventType("dump_notification"), 0x08);
+    EXPECT_THROW(getEventType("foo"), std::runtime_error);
+
+    EXPECT_EQ(getEventScope("possibly_multiple_platforms"), 0x04);
+    EXPECT_THROW(getEventScope("foo"), std::runtime_error);
+
+    std::vector<std::string> flags{"service_action", "dont_report",
+                                   "termination"};
+    EXPECT_EQ(getActionFlags(flags), 0x9100);
+
+    flags.clear();
+    flags.push_back("foo");
+    EXPECT_THROW(getActionFlags(flags), std::runtime_error);
+}