diff --git a/presence/test/Makefile.am b/presence/test/Makefile.am
index 56c3ab3..e4fe930 100644
--- a/presence/test/Makefile.am
+++ b/presence/test/Makefile.am
@@ -5,3 +5,18 @@
 check_PROGRAMS =
 
 TESTS = $(check_PROGRAMS)
+
+check_PROGRAMS += fallbacktest
+fallbacktest_SOURCES = \
+	fallbacktest.cpp
+fallbacktest_CXXFLAGS = \
+	$(gtest_cflags) \
+	${PHOSPHOR_DBUS_INTERFACES_CFLAGS} \
+	$(SDBUSPLUS_CFLAGS)
+fallbacktest_LDFLAGS = \
+	$(OESDK_TESTCASE_FLAGS)
+fallbacktest_LDADD = \
+	${builddir}/../fallback.o \
+	$(gtest_ldadd) \
+	${PHOSPHOR_DBUS_INTERFACES_LIBS} \
+	$(SDBUSPLUS_LIBS)
diff --git a/presence/test/fallbacktest.cpp b/presence/test/fallbacktest.cpp
new file mode 100644
index 0000000..a9f989c
--- /dev/null
+++ b/presence/test/fallbacktest.cpp
@@ -0,0 +1,234 @@
+#include <iostream>
+#include <string>
+#include <gtest/gtest.h>
+#include "../fallback.hpp"
+#include "../psensor.hpp"
+
+int pstate = -1;
+
+namespace phosphor
+{
+namespace fan
+{
+namespace presence
+{
+void setPresence(const Fan& fan, bool newState)
+{
+    if (newState)
+    {
+        pstate = 1;
+    }
+    else
+    {
+        pstate = 0;
+    }
+}
+
+class TestSensor : public PresenceSensor
+{
+    public:
+        bool start() override
+        {
+            ++started;
+            return _present;
+        }
+
+        void stop() override
+        {
+            ++stopped;
+        }
+
+        bool present() override
+        {
+            return _present;
+        }
+
+        void fail() override
+        {
+            ++failed;
+        }
+
+        bool _present = false;
+        size_t started = 0;
+        size_t stopped = 0;
+        size_t failed = 0;
+};
+
+} // namespace presence
+} // namespace fan
+} // namespace phosphor
+
+using namespace phosphor::fan::presence;
+
+TEST(FallbackTest, TestOne)
+{
+    // Validate a single sensor.
+    // Validate on->off->on.
+    pstate = -1;
+    Fan fan{"/path", "name"};
+    TestSensor ts;
+    ts._present = true;
+    std::vector<std::reference_wrapper<PresenceSensor>> sensors{ts};
+    Fallback f{fan, sensors};
+
+    f.monitor();
+    ASSERT_EQ(pstate, 1);
+    ASSERT_EQ(ts.failed, 0);
+    ASSERT_EQ(ts.stopped, 0);
+    ASSERT_EQ(ts.started, 1);
+
+    f.stateChanged(false);
+    ASSERT_EQ(pstate, 0);
+    ASSERT_EQ(ts.failed, 0);
+    ASSERT_EQ(ts.stopped, 0);
+    ASSERT_EQ(ts.started, 1);
+
+    f.stateChanged(true);
+    ASSERT_EQ(pstate, 1);
+    ASSERT_EQ(ts.failed, 0);
+    ASSERT_EQ(ts.stopped, 0);
+    ASSERT_EQ(ts.started, 1);
+}
+
+TEST(FallbackTest, TestTwoA)
+{
+    // Validate two sensors.
+    // Validate both sensors on->off->on
+
+    pstate = -1;
+    Fan fan{"/path", "name"};
+    TestSensor ts1, ts2;
+    ts1._present = true;
+    ts2._present = true;
+
+    std::vector<std::reference_wrapper<PresenceSensor>> sensors{ts1, ts2};
+    Fallback f{fan, sensors};
+
+    f.monitor();
+    ASSERT_EQ(pstate, 1);
+    ASSERT_EQ(ts1.failed, 0);
+    ASSERT_EQ(ts1.stopped, 0);
+    ASSERT_EQ(ts1.started, 1);
+    ASSERT_EQ(ts2.failed, 0);
+    ASSERT_EQ(ts2.stopped, 0);
+    ASSERT_EQ(ts2.started, 0);
+
+    ts1._present = false;
+    ts2._present = false;
+    f.stateChanged(false);
+    ASSERT_EQ(pstate, 0);
+    ASSERT_EQ(ts1.failed, 0);
+    ASSERT_EQ(ts1.stopped, 0);
+    ASSERT_EQ(ts1.started, 1);
+    ASSERT_EQ(ts2.failed, 0);
+    ASSERT_EQ(ts2.stopped, 0);
+    ASSERT_EQ(ts2.started, 0);
+
+    ts1._present = true;
+    ts2._present = true;
+    f.stateChanged(true);
+    ASSERT_EQ(pstate, 1);
+    ASSERT_EQ(ts1.failed, 0);
+    ASSERT_EQ(ts1.stopped, 0);
+    ASSERT_EQ(ts1.started, 1);
+    ASSERT_EQ(ts2.failed, 0);
+    ASSERT_EQ(ts2.stopped, 0);
+    ASSERT_EQ(ts2.started, 0);
+}
+
+
+TEST(FallbackTest, TestTwoB)
+{
+    // Validate two sensors.
+    // Validate first sensor on->off.
+
+    pstate = -1;
+    Fan fan{"/path", "name"};
+    TestSensor ts1, ts2;
+    ts1._present = true;
+    ts2._present = true;
+
+    std::vector<std::reference_wrapper<PresenceSensor>> sensors{ts1, ts2};
+    Fallback f{fan, sensors};
+
+    f.monitor();
+    ASSERT_EQ(pstate, 1);
+    ts1._present = false;
+    f.stateChanged(false);
+    ASSERT_EQ(pstate, 1);
+    ASSERT_EQ(ts1.failed, 1);
+    ASSERT_EQ(ts1.stopped, 1);
+    ASSERT_EQ(ts1.started, 1);
+    ASSERT_EQ(ts2.failed, 0);
+    ASSERT_EQ(ts2.stopped, 0);
+    ASSERT_EQ(ts2.started, 1);
+
+    // Flip the state of both sensors.
+    ts1._present = true;
+    ts2._present = false;
+    f.stateChanged(false);
+    ASSERT_EQ(pstate, 0);
+    ASSERT_EQ(ts1.failed, 1);
+    ASSERT_EQ(ts1.stopped, 1);
+    ASSERT_EQ(ts1.started, 1);
+    ASSERT_EQ(ts2.failed, 0);
+    ASSERT_EQ(ts2.stopped, 0);
+    ASSERT_EQ(ts2.started, 1);
+}
+
+TEST(FallbackTest, TestTwoC)
+{
+    // Validate two sensors.
+    // Validate first in bad state.
+
+    pstate = -1;
+    Fan fan{"/path", "name"};
+    TestSensor ts1, ts2;
+    ts1._present = false;
+    ts2._present = true;
+
+    std::vector<std::reference_wrapper<PresenceSensor>> sensors{ts1, ts2};
+    Fallback f{fan, sensors};
+
+    f.monitor();
+    ASSERT_EQ(pstate, 1);
+    ASSERT_EQ(ts1.failed, 1);
+    ASSERT_EQ(ts1.stopped, 0);
+    ASSERT_EQ(ts1.started, 0);
+    ASSERT_EQ(ts2.failed, 0);
+    ASSERT_EQ(ts2.stopped, 0);
+    ASSERT_EQ(ts2.started, 1);
+
+    f.stateChanged(false);
+    ASSERT_EQ(pstate, 0);
+    ASSERT_EQ(ts1.failed, 1);
+    ASSERT_EQ(ts1.stopped, 0);
+    ASSERT_EQ(ts1.started, 0);
+    ASSERT_EQ(ts2.failed, 0);
+    ASSERT_EQ(ts2.stopped, 0);
+    ASSERT_EQ(ts2.started, 1);
+}
+
+TEST(FallbackTest, TestTwoD)
+{
+    // Validate two sensors.
+    // Validate both in bad state.
+
+    pstate = -1;
+    Fan fan{"/path", "name"};
+    TestSensor ts1, ts2;
+    ts1._present = false;
+    ts2._present = false;
+
+    std::vector<std::reference_wrapper<PresenceSensor>> sensors{ts1, ts2};
+    Fallback f{fan, sensors};
+
+    f.monitor();
+    ASSERT_EQ(pstate, 0);
+    ASSERT_EQ(ts1.failed, 0);
+    ASSERT_EQ(ts1.stopped, 0);
+    ASSERT_EQ(ts1.started, 1);
+    ASSERT_EQ(ts2.failed, 0);
+    ASSERT_EQ(ts2.stopped, 0);
+    ASSERT_EQ(ts2.started, 0);
+}