diff --git a/test/pid_fancontroller_unittest.cpp b/test/pid_fancontroller_unittest.cpp
new file mode 100644
index 0000000..b127929
--- /dev/null
+++ b/test/pid_fancontroller_unittest.cpp
@@ -0,0 +1,237 @@
+#include "pid/fancontroller.hpp"
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+#include <string>
+#include <vector>
+
+#include "pid/ec/pid.hpp"
+#include "test/sensor_mock.hpp"
+#include "test/zone_mock.hpp"
+
+using ::testing::DoubleEq;
+using ::testing::Invoke;
+using ::testing::Return;
+using ::testing::StrEq;
+using ::testing::_;
+
+TEST(FanControllerTest, BoringFactoryTest) {
+    // Verify the factory will properly build the FanPIDController in the
+    // boring (uninteresting) case.
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fan0"};
+    ec::pidinfo initial;
+
+    std::unique_ptr<PIDController> p =
+        FanController::CreateFanPid(&z, "fan1", inputs, initial);
+    // Success
+    EXPECT_FALSE(p == nullptr);
+}
+
+TEST(FanControllerTest, VerifyFactoryFailsWithZeroInputs) {
+    // A fan controller needs at least one input.
+
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {};
+    ec::pidinfo initial;
+
+    std::unique_ptr<PIDController> p =
+        FanController::CreateFanPid(&z, "fan1", inputs, initial);
+    EXPECT_TRUE(p == nullptr);
+}
+
+TEST(FanControllerTest, InputProc_AllSensorsReturnZero) {
+    // If all your inputs are 0, return 0.
+
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fan0", "fan1"};
+    ec::pidinfo initial;
+
+    std::unique_ptr<PIDController> p =
+        FanController::CreateFanPid(&z, "fan1", inputs, initial);
+    EXPECT_FALSE(p == nullptr);
+
+    EXPECT_CALL(z, getCachedValue(StrEq("fan0"))).WillOnce(Return(0));
+    EXPECT_CALL(z, getCachedValue(StrEq("fan1"))).WillOnce(Return(0));
+
+    EXPECT_EQ(0.0, p->input_proc());
+}
+
+TEST(FanControllerTest, InputProc_IfSensorNegativeIsIgnored) {
+    // A sensor value returning sub-zero is ignored as an error.
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fan0", "fan1"};
+    ec::pidinfo initial;
+
+    std::unique_ptr<PIDController> p =
+        FanController::CreateFanPid(&z, "fan1", inputs, initial);
+    EXPECT_FALSE(p == nullptr);
+
+    EXPECT_CALL(z, getCachedValue(StrEq("fan0"))).WillOnce(Return(-1));
+    EXPECT_CALL(z, getCachedValue(StrEq("fan1"))).WillOnce(Return(-1));
+
+    EXPECT_EQ(0.0, p->input_proc());
+}
+
+TEST(FanControllerTest, InputProc_ChoosesMinimumValue) {
+    // Verify it selects the minimum value from its inputs.
+
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fan0", "fan1", "fan2"};
+    ec::pidinfo initial;
+
+    std::unique_ptr<PIDController> p =
+        FanController::CreateFanPid(&z, "fan1", inputs, initial);
+    EXPECT_FALSE(p == nullptr);
+
+    EXPECT_CALL(z, getCachedValue(StrEq("fan0"))).WillOnce(Return(10.0));
+    EXPECT_CALL(z, getCachedValue(StrEq("fan1"))).WillOnce(Return(30.0));
+    EXPECT_CALL(z, getCachedValue(StrEq("fan2"))).WillOnce(Return(5.0));
+
+    EXPECT_EQ(5.0, p->input_proc());
+}
+
+// The direction is unused presently, but these tests validate the logic.
+TEST(FanControllerTest, SetPtProc_SpeedChanges_VerifyDirection) {
+    // The fan direction defaults to neutral, because we have no data.  Verify
+    // that after this point it appropriately will indicate speeding up or
+    // slowing down based on the RPM values specified.
+
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fan0", "fan1"};
+    ec::pidinfo initial;
+
+    std::unique_ptr<PIDController> p =
+        FanController::CreateFanPid(&z, "fan1", inputs, initial);
+    EXPECT_FALSE(p == nullptr);
+    // Grab pointer for mocking.
+    FanController *fp = reinterpret_cast<FanController*>(p.get());
+
+    // Fanspeed starts are Neutral.
+    EXPECT_EQ(FanSpeedDirection::NEUTRAL, fp->getFanDirection());
+
+    // getMaxRPMRequest returns a higher value than 0, so the fans should be
+    // marked as speeding up.
+    EXPECT_CALL(z, getMaxRPMRequest()).WillOnce(Return(10.0));
+    EXPECT_EQ(10.0, p->setpt_proc());
+    EXPECT_EQ(FanSpeedDirection::UP, fp->getFanDirection());
+
+    // getMaxRPMRequest returns a lower value than 10, so the fans should be
+    // marked as slowing down.
+    EXPECT_CALL(z, getMaxRPMRequest()).WillOnce(Return(5.0));
+    EXPECT_EQ(5.0, p->setpt_proc());
+    EXPECT_EQ(FanSpeedDirection::DOWN, fp->getFanDirection());
+
+    // getMaxRPMRequest returns the same value, so the fans should be marked as
+    // neutral.
+    EXPECT_CALL(z, getMaxRPMRequest()).WillOnce(Return(5.0));
+    EXPECT_EQ(5.0, p->setpt_proc());
+    EXPECT_EQ(FanSpeedDirection::NEUTRAL, fp->getFanDirection());
+}
+
+TEST(FanControllerTest, OutputProc_VerifiesIfFailsafeEnabledInputIsIgnored) {
+    // Verify that if failsafe mode is enabled and the input value for the fans
+    // is below the failsafe minimum value, the input is not used and the fans
+    // are driven at failsafe RPM.
+
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fan0", "fan1"};
+    ec::pidinfo initial;
+
+    std::unique_ptr<PIDController> p =
+        FanController::CreateFanPid(&z, "fan1", inputs, initial);
+    EXPECT_FALSE(p == nullptr);
+
+    EXPECT_CALL(z, getFailSafeMode()).WillOnce(Return(true));
+    EXPECT_CALL(z, getFailSafePercent()).Times(2).WillRepeatedly(Return(75.0));
+
+    int64_t timeout = 0;
+    std::unique_ptr<Sensor> s1 = std::make_unique<SensorMock>("fan0", timeout);
+    std::unique_ptr<Sensor> s2 = std::make_unique<SensorMock>("fan1", timeout);
+    // Grab pointers for mocking.
+    SensorMock *sm1 = reinterpret_cast<SensorMock*>(s1.get());
+    SensorMock *sm2 = reinterpret_cast<SensorMock*>(s2.get());
+
+    EXPECT_CALL(z, getSensor(StrEq("fan0"))).WillOnce(Return(s1.get()));
+    EXPECT_CALL(*sm1, write(0.75));
+    EXPECT_CALL(z, getSensor(StrEq("fan1"))).WillOnce(Return(s2.get()));
+    EXPECT_CALL(*sm2, write(0.75));
+
+    // This is a fan PID, so calling output_proc will try to write this value
+    // to the sensors.
+
+    // Setting 50%, will end up being 75% because the sensors are in failsafe mode.
+    p->output_proc(50.0);
+}
+
+TEST(FanControllerTest, OutputProc_BehavesAsExpected) {
+    // Verifies that when the system is not in failsafe mode, the input value
+    // to output_proc is used to drive the sensors (fans).
+
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fan0", "fan1"};
+    ec::pidinfo initial;
+
+    std::unique_ptr<PIDController> p =
+        FanController::CreateFanPid(&z, "fan1", inputs, initial);
+    EXPECT_FALSE(p == nullptr);
+
+    EXPECT_CALL(z, getFailSafeMode()).WillOnce(Return(false));
+
+    int64_t timeout = 0;
+    std::unique_ptr<Sensor> s1 = std::make_unique<SensorMock>("fan0", timeout);
+    std::unique_ptr<Sensor> s2 = std::make_unique<SensorMock>("fan1", timeout);
+    // Grab pointers for mocking.
+    SensorMock *sm1 = reinterpret_cast<SensorMock*>(s1.get());
+    SensorMock *sm2 = reinterpret_cast<SensorMock*>(s2.get());
+
+    EXPECT_CALL(z, getSensor(StrEq("fan0"))).WillOnce(Return(s1.get()));
+    EXPECT_CALL(*sm1, write(0.5));
+    EXPECT_CALL(z, getSensor(StrEq("fan1"))).WillOnce(Return(s2.get()));
+    EXPECT_CALL(*sm2, write(0.5));
+
+    // This is a fan PID, so calling output_proc will try to write this value
+    // to the sensors.
+    p->output_proc(50.0);
+}
+
+TEST(FanControllerTest, OutputProc_VerifyFailSafeIgnoredIfInputHigher) {
+    // If the requested output is higher than the failsafe value, then use the
+    // value provided to output_proc.
+
+    ZoneMock z;
+
+    std::vector<std::string> inputs = {"fan0"};
+    ec::pidinfo initial;
+
+    std::unique_ptr<PIDController> p =
+        FanController::CreateFanPid(&z, "fan1", inputs, initial);
+    EXPECT_FALSE(p == nullptr);
+
+    EXPECT_CALL(z, getFailSafeMode()).WillOnce(Return(true));
+    EXPECT_CALL(z, getFailSafePercent()).WillOnce(Return(75.0));
+
+    int64_t timeout = 0;
+    std::unique_ptr<Sensor> s1 = std::make_unique<SensorMock>("fan0", timeout);
+    // Grab pointer for mocking.
+    SensorMock *sm1 = reinterpret_cast<SensorMock*>(s1.get());
+
+    // Converting from float to double for expectation.
+    float percent = 80;
+    double value = static_cast<double>(percent / 100);
+
+    EXPECT_CALL(z, getSensor(StrEq("fan0"))).WillOnce(Return(s1.get()));
+    EXPECT_CALL(*sm1, write(value));
+
+    // This is a fan PID, so calling output_proc will try to write this value
+    // to the sensors.
+    p->output_proc(percent);
+}