[examples] AddressableLED: Add unit test (#4779)

wpilibcExamples/src/main/cpp/examples/AddressableLED/include/Robot.h

@@ -0,0 +1,28 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <array>
+
+#include <frc/AddressableLED.h>
+#include <frc/TimedRobot.h>
+
+class Robot : public frc::TimedRobot {
+ public:
+  void Rainbow();
+  void RobotInit() override;
+  void RobotPeriodic() override;
+
+ private:
+  static constexpr int kLength = 60;
+
+  // PWM port 9
+  // Must be a PWM header, not MXP or DIO
+  frc::AddressableLED m_led{9};
+  std::array<frc::AddressableLED::LEDData, kLength>
+      m_ledBuffer;  // Reuse the buffer
+  // Store what the last hue of the first pixel is
+  int firstPixelHue = 0;
+};