Bash shell if operator

I write a function like this to .commands file, and I imported .commands in .zshrc

function testA() {
  echo "start"
  if [ "$1" == "a" ]; then
    echo "ok"
  fi
  echo "end"
}

And when I run testA a in terminal

start
testA:2: = not found

What is the problem here?

>Solution :

Chapter 12 – "Conditional Expressions" of the zsh documentation states:

A conditional expression is used with the [[ compound command to test attributes of files and to compare strings.

This means, changing your conditional expression to use [[ ... ]] instead of [ ... ] should make it work:

function testA() {
  echo "start"
  if [[ "$1" == "a" ]]; then
    echo "ok"
  fi
  echo "end"
}