### Question:
UnitConverter { public static long convertSecondsToNanoseconds(double seconds) { return (long) (seconds * 1000000000L); } private  UnitConverter(); static long convertSecondsToNanoseconds(double seconds); static long convertSecondsToNanoseconds(long seconds);  }### Answer:
@Test public void testConversion() { assertEquals(UnitConverter.convertSecondsToNanoseconds(-1), -1000000000L); assertEquals(UnitConverter.convertSecondsToNanoseconds(0), 0L); assertEquals(UnitConverter.convertSecondsToNanoseconds(7), 7000000000L); assertEquals(UnitConverter.convertSecondsToNanoseconds(-1.34), -1340000000L); assertEquals(UnitConverter.convertSecondsToNanoseconds(0.0), 0L); assertEquals(UnitConverter.convertSecondsToNanoseconds(6.99), 6990000000L); }