expect is a great program for driving interactive programs however you choose, check this out.

Here is test.expect:

spawn bash

set timeout 1

send "echo input1 | rev\n"
expect {
  "1tupni" {
    puts "Got 1tupni!"
  }
  timeout {
    puts "didn't get 1tupni soon enough..."
    exit 1
  }
}


send "echo input2 | rev\n"
expect {
  "2tupni" {
    puts "Got 2tupni!"
  }
  timeout {
    puts "didn't get 2tupni soon enough..."
    exit 1
  }
}

# Note I used `input3` here but look for `input4` 
send "echo input3 | rev\n"
expect {
  "4tupni" {
    puts "Got 4tupni!"
  }
  timeout {
    puts "didn't get 4tupni soon enough..."
    exit 1
  }
}

exit 0

And running it:

Morbo> expect ./test.expect
spawn bash
echo input1 | rev

[grahamc@Morbo:~/projects/student-programs]$ echo input1 | rev
1tupni
Got 1tupni!
echo input2 | rev

[grahamc@Morbo:~/projects/student-programs]$ echo input2 | rev
2tupni
Got 2tupni!
echo input3 | rev

[grahamc@Morbo:~/projects/student-programs]$ echo input3 | rev
3tupni

[grahamc@Morbo:~/projects/student-programs]$ didn't get 4tupni soon enough...
Morbo> echo $?
1