package main

import (
	"bufio"
	"fmt"
	"os"
	"strings"
)

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	var t int
	fmt.Sscan(scanner.Text(), &t)
	for test := 0; test < t; test++ {
		scanner.Scan()
		parts := strings.Fields(scanner.Text())
		s := parts[0]
		c := parts[1]
		if s < c {
			fmt.Println(s)
			continue
		}
		n := len(s)
		l := len(c)
		pp := 0
		mm := min(n, l)
		for pp < mm && s[pp] == c[pp] {
			pp++
		}
		found := false
		var news string
		for q := 0; q < pp; q++ {
			target := s[q]
			for kk := q + 1; kk < n; kk++ {
				if s[kk] < target {
					bs := []byte(s)
					bs[q], bs[kk] = bs[kk], bs[q]
					news = string(bs)
					found = true
					break
				}
			}
			if found {
				break
			}
		}
		if !found && pp < mm {
			target := c[pp]
			for kk := pp + 1; kk < n; kk++ {
				if s[kk] < target {
					bs := []byte(s)
					bs[pp], bs[kk] = bs[kk], bs[pp]
					news = string(bs)
					found = true
					break
				}
			}
			if !found {
				for kk := pp + 1; kk < n; kk++ {
					if s[kk] == target {
						isSmaller := false
						pos := 0
						stopped := false
						for pos < n && pos < l && !stopped {
							var ch byte
							if pos == pp {
								ch = s[kk]
							} else if pos == kk {
								ch = s[pp]
							} else {
								ch = s[pos]
							}
							if ch != c[pos] {
								if ch < c[pos] {
									isSmaller = true
								}
								stopped = true
							}
							pos++
						}
						if !stopped {
							if n < l {
								isSmaller = true
							}
						}
						if isSmaller {
							bs := []byte(s)
							bs[pp], bs[kk] = bs[kk], bs[pp]
							news = string(bs)
							found = true
							break
						}
					}
				}
			}
		}
		if found {
			fmt.Println(news)
		} else {
			fmt.Println("---")
		}
	}
}