### Question:
LatLonPoints { public static double lonDiff(double lon1, double lon2) { return Math.IEEEremainder(lon1 - lon2, 360.0); }  static boolean betweenLon(double lon, double lonBeg, double lonEnd); static double lonNormal360(double lon); static double lonNormal(double lon, double center); static double lonNormalFrom(double lon, double start); static double lonNormal(double lon); static double lonDiff(double lon1, double lon2); static double latNormal(double lat); static String latToString(double lat, int ndec); static String lonToString(double lon, int ndec); static boolean isInfinite(ProjectionPoint pt); static double range180(double lon); static String toString(LatLonPoint pt, int sigDigits); static String toString(ProjectionPoint pt, int sigDigits);  }### Answer:
@Test public void testLonDiff() { assertThat(LatLonPoints.lonDiff(90, 89)).isEqualTo(1); assertThat(LatLonPoints.lonDiff(90, 99)).isEqualTo(-9); assertThat(LatLonPoints.lonDiff(90 - 360, 89 + 360)).isEqualTo(1); assertThat(LatLonPoints.lonDiff(90 - 360, 99 + 360)).isEqualTo(-9); }