You don't need any of those to write an if statement. I frequently write if statements like this one

    if ! grep -qF something /etc/some/config/file 2>/dev/null; then
      do_something
    fi

The `test` command is there if you want to use it, but it's just another command.

In the case of Bash, `test` is a built-in command rather than an external program, and it also has two other names, `[` and `[[`. I don't like the latter two because they look, to a naive reader, like special syntax built into the shell— like something the parser sees as unique and different and bear a special relationship to if-statements— but they aren't and they don't. And in fact you can use them in other shells that don't have them as built-ins, if you implement them as external commands. (You can probably find a binary called `[` on your system right now.)

(Actually, it looks like `[[` is even worse than "fake syntax"... it's real special syntax. It changes how Bash interprets `&&` and `||`. Yikes.)

But if you don't like `test`, you don't have to use it; you can use any command you like!

For instance, you might use `expr`:

  if expr "1 > 0"; then
    echo this will always run
  else
    echo this will never run
  fi

Fish has some built-ins that fall into a similar niche that are handy for simple comparisons like this, namely `math` and `string`, but there are probably others.

If you really don't like `test`, don't even need to use it for checking the existence or type (dir, symlink, socket, etc.) of files! You can use GNU `find` for that, or even sharkdp's `fd` if you ache for something new and shiny.

Fish actually has something really nice here in the `path` built-in, which includes long options like you and I both wish `test` had. You can write:

  if path -q --type=dir a/b/c
    touch a/b/c/some-file
  end

You don't need `test` for asking about or asserting equality of variables, either;

  grep -qxF "$A" <<< "$B"

is equivalent to

  test "A" = "$B"

or with the Fish `string` built-in

  string match --entire $A $B

The key is that in a shell, all commands are truthy in terms of their exit status. `&&` and `||` let you combine those exit statuses in exactly the way you'd expect, as do the (imo much more elegant) `and` and `or` combiner commands in Fish.

Finally, there's no need to use the likes of `test` for combining conditions. I certainly never do. You can just write

  test "$A" = "$B" && test "$C" = "$D"

instead of something like

  [ "$A" = "$B" -a "$C" = "$D" ]

If-statements in shell languages are so simple that there's practically nothing to them. They just take a single command (any!) and branch based on its exit status! That's it.

As for readability: any program in any language is difficult to understand if you don't know the interfaces or behaviors of the functions it invokes. `[`/`test` is no different from any such function, although it appears that `[[` is something weirder and, imo, worse.