platformio native unit test Arduino.h not found

Question

I'm writing code for a microcontroller project using PlatformIO.

I have a couple of classes that I want to write unit tests for. I've not unit tested with pio before so I'm starting with one of the easier classes. I wrote out the start of my test:

#include "PixelRange.h"
#include <unity.h>
void test_forward_incrementation(void)
{
  PixelRange range = PixelRange(1, 5, 10);
  uint8_t currentIndex = range.getCurrentIndex();
TEST_ASSERT_EQUAL(5, currentIndex);
}
int main(int argc, char **argv)
{
  UNITY_BEGIN();
  RUN_TEST(test_forward_incrementation);
  UNITY_END();
  return 0;
}

For my class:

#pragma once
#include <Arduino.h>
class PixelRange
{
public:
  PixelRange() {}
  PixelRange(int rows, int startingIndex, int endingIndex);
void setReverseIteration(bool reverse);
  uint8_t getNextIndex();
  uint8_t getCurrentIndex();
int getRowCount();
  int getStart();
  int getEnd();
private:
  bool _iterateInReverse = false;
  uint8_t _iteratorIndex = 0;
  int _rowCount;
  int _start;
  int _end;
uint8_t forwardIteration();
  uint8_t reverseIteration();
};

And my platform.ini looks like this:

[env:adafruit_trinket_m0]
platform = atmelsam
board = adafruit_trinket_m0
framework = arduino
lib_deps = fastled/FastLED@^3.4.0
[env:native]
platform = native
test_ignore = test_embedded

I wanted to start by running the test in the native environment, but when I run it I get errors saying that I'm missing the Arduino.h file. Even odder, one of the errors is coming from a file that's not even under test.

I'm referring to the calculator example as far as setup and I don't see anywhere in the desktop test where Arduino.h is mocked.

Anyone have an idea of why this would be failing? Here's the full project in case that helps.