### Question:
Preconditions { public static void checkState( boolean expression, String message ) { if ( !expression ) { throw new IllegalStateException( message ); } } private  Preconditions(); static long requirePositive( long value ); static long requirePowerOfTwo( long value ); static int requirePositive( int value ); static long requireNonNegative( long value ); static int requireNonNegative( int value ); static int requireExactlyZero( int value ); static void checkState( boolean expression, String message ); static void checkArgument( boolean expression, String message, Object... args ); static void requireBetween( int value, int lowInclusive, int highExclusive );  }### Answer:
@Test void checkStateOk() { Preconditions.checkState( true, "must not fail" ); }
@Test void checkStateFails() { assertThrows( IllegalStateException.class, () -> Preconditions.checkState( false, "must fail" ) ); }