unexpected regex match

Question

Hi,

Can anyone explain why the following test is not passing. The regex is getting a match where I do not want one.

I want to find a match on text that begins with Tel, Fax or Web but for some reason, the url in the test is getting a match:

  def test_url_should_match
    assert_no_match(/^[tel|fax|web]/i, "www.jehall.co.uk")
  end

Thanks for your help.

Paul

Answer 1

You should use

/^(?:tel|fax|web)/i

Answer 2

Try it with

assert_no_match(/^(tel|fax|web)/i, "www.jehall.co.uk")

That should work. Otherwise you're matching against the characters, i.e. the w in web will match.

Answer 3

[...] in a regular expression specifies a character class, which tells the regular expression engine to match one of these characters contained within brackets. Therefore, [tel|fax|web] means "match t or e or l or | or f or a or x or w or e or b" (the fact that | appears more than once in the class is irrelevant). Since the string starts with a w -- which is in the character class -- the pattern matches.

As other answers have said, you want to use parentheses (...) to group your alternation instead.