how do i test instances in junit?

**This is what I want to test public class EPATestMode {

  public static final int INVALID_MPG = -1; 

  private int odometerAtReset;


  public EPATestMode() {
    odometerAtReset = 0;
  }


  public void resetReadings(int milesDriven) {
    // Use the current mileage as the new baseline
    odometerAtReset = milesDriven;
  }


  public double mpg(int currentOdometer, int gallonsBurnt) {
    if (gallonsBurnt == 0) {
      return INVALID_MPG;
    } else {

      int milesDriven = currentOdometer - odometerAtReset;

      return milesDriven / gallonsBurnt;
    }
  }
}

this is my first testcase I want to do , on the instance variable INvalid MPG but when I do this , there is a line crossing out "assertEquals". Very confused about this.(Also new to JUnit testing)

@Test
public void testInvalidMpg() {
    EPATestMode MpgTest = new EPATestMode();
    double results=MpgTest.INVALID_MPG;
    assertEquals(results,-1)

}