diff --git a/test/Makefile.am b/test/Makefile.am
index c46284f..fb1d58d 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -17,7 +17,8 @@
  sensor_host_unittest util_unittest pid_zone_unittest \
  pid_thermalcontroller_unittest pid_fancontroller_unittest \
  pid_stepwisecontroller_unittest \
- dbus_passive_unittest dbus_active_unittest
+ dbus_passive_unittest dbus_active_unittest \
+ sensors_json_unittest
 TESTS = $(check_PROGRAMS)
 
 # Until libconfig is mocked out or replaced, include it.
@@ -58,3 +59,6 @@
 
 dbus_active_unittest_SOURCES = dbus_active_unittest.cpp
 dbus_active_unittest_LDADD = $(top_builddir)/dbus/dbusactiveread.o
+
+sensors_json_unittest_SOURCES = sensors_json_unittest.cpp
+sensors_json_unittest_LDADD = $(top_builddir)/sensors/buildjson.o
diff --git a/test/sensors_json_unittest.cpp b/test/sensors_json_unittest.cpp
new file mode 100644
index 0000000..99ab3db
--- /dev/null
+++ b/test/sensors_json_unittest.cpp
@@ -0,0 +1,100 @@
+#include "sensors/buildjson.hpp"
+#include "sensors/sensor.hpp"
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+TEST(SensorsFromJson, emptyJsonNoSensors)
+{
+    // If the json has no sensors, the map is empty.
+
+    auto j2 = R"(
+      {
+        "sensors": []
+      }
+    )"_json;
+
+    auto output = buildSensorsFromJson(j2);
+    EXPECT_TRUE(output.empty());
+}
+
+TEST(SensorsFromJson, oneFanSensor)
+{
+    // If the json has one sensor, it's in the map.
+
+    auto j2 = R"(
+      {
+        "sensors": [{
+            "name": "fan1",
+            "type": "fan",
+            "readpath": "/xyz/openbmc_project/sensors/fan_tach/fan1",
+            "writepath": "/sys/devices/platform/ahb/ahb:apb/1e786000.pwm-tacho-controller/hwmon/**/pwm1",
+            "min": 0,
+            "max": 255
+        }]
+      }
+    )"_json;
+
+    auto output = buildSensorsFromJson(j2);
+    EXPECT_EQ(1, output.size());
+    EXPECT_EQ(output["fan1"].type, "fan");
+    EXPECT_EQ(output["fan1"].readpath,
+              "/xyz/openbmc_project/sensors/fan_tach/fan1");
+    EXPECT_EQ(output["fan1"].writepath,
+              "/sys/devices/platform/ahb/ahb:apb/1e786000.pwm-tacho-controller/"
+              "hwmon/**/pwm1");
+    EXPECT_EQ(output["fan1"].min, 0);
+    EXPECT_EQ(output["fan1"].max, 255);
+    EXPECT_EQ(output["fan1"].timeout,
+              Sensor::getDefaultTimeout(output["fan1"].type));
+}
+
+TEST(SensorsFromJson, validateOptionalFields)
+{
+    // The writepath, min, max, timeout fields are optional.
+
+    auto j2 = R"(
+      {
+        "sensors": [{
+            "name": "fan1",
+            "type": "fan",
+            "readpath": "/xyz/openbmc_project/sensors/fan_tach/fan1"
+        }]
+      }
+    )"_json;
+
+    auto output = buildSensorsFromJson(j2);
+    EXPECT_EQ(1, output.size());
+    EXPECT_EQ(output["fan1"].type, "fan");
+    EXPECT_EQ(output["fan1"].readpath,
+              "/xyz/openbmc_project/sensors/fan_tach/fan1");
+    EXPECT_EQ(output["fan1"].writepath, "");
+    EXPECT_EQ(output["fan1"].min, 0);
+    EXPECT_EQ(output["fan1"].max, 0);
+    EXPECT_EQ(output["fan1"].timeout,
+              Sensor::getDefaultTimeout(output["fan1"].type));
+}
+
+TEST(SensorsFromJson, twoSensors)
+{
+    // Same as one sensor, but two.
+    // If a configuration has two sensors with the same name the information
+    // last is the information used.
+
+    auto j2 = R"(
+      {
+        "sensors": [{
+            "name": "fan1",
+            "type": "fan",
+            "readpath": "/xyz/openbmc_project/sensors/fan_tach/fan1"
+        }, {
+            "name": "fan2",
+            "type": "fan",
+            "readpath": "/xyz/openbmc_project/sensors/fan_tach/fan1"
+        }]
+      }
+    )"_json;
+
+    auto output = buildSensorsFromJson(j2);
+    EXPECT_EQ(2, output.size());
+}