#!/usr/bin/perl

$i1 = <>;
chomp($i1);
for ($count = 0; $count < $i1; $count++) {
 	$i2 = <>;
	$i3 = <>;
	chomp $i2;
        chomp $i3;
	my @values;
	@values = split(/ /, $i3);

	my @differences;
	my $count1;
	my $count2;
	my $min;

	for ($count1 = 0; $count1 < $i2; $count++) {
		for ($count2 = $count1+1; $count2<$i2; $count2++) {
			if($count1 = 0 and $count2 = 1)
			{
				$min =abs($values[$count1]-$values[$count2]);
			}
			elsif($min> abs($values[$count1]-$values[$count2]))
			{
				$min = abs($values[$count1]-$values[$count2]);
			}
		}
	}
	print $min;
}