fn test_str() {
    let s = "Hello World"

    assert_eq(#s, 11)

    $s += "!"
    assert_eq(#s, 12)

    assert_eq($s.to_upper(), "HELLO WORLD!")
    assert_eq("FOO".to_lower(), "foo")

    assert("ello" in $s)

    assert_eq("%s, %d!".format("Hello", 2025), "Hello, 2025!")

    assert_eq(str::from_bool(true), "true")
    assert_eq(" Hello ".trim(), "Hello")
}