Exclude part of a String during pattern matching in Scala

Question

I have a simple enough problem. In my unit test I compare expected vs actual output as a String value. Now part of the string is a randomly generated unique ID which causes the test to fail every time. Is there a way I can specify my test to only match part of the actual and ignore text between two points in the string. A function like -

def isMatch(expected : String, actual : String , ignoreFrom : String , ignoreTo : String)

Also, since this is a candidate for pattern matching, could some one point me to a pattern match/regex for Dummies kind of a tutorial?

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Engineer
– Engineer

2013-10-11 07:57:23 +00:00
Commented Oct 11, 2013 at 7:57 — Engineer
– Engineer, Commented Oct 11, 2013 at 7:57
ignoreFrom is String or Int?

Andrzej Jozwik
– Andrzej Jozwik

2013-10-11 08:41:18 +00:00
Commented Oct 11, 2013 at 8:41 — Andrzej Jozwik
– Andrzej Jozwik, Commented Oct 11, 2013 at 8:41

Eddie Jamsession · Accepted Answer · 2013-10-11 09:35:16Z

2

I think Scala extractors is what you want. You can specify extractor to match only specific part of the string.

Here is some example:

object IgnoreBetween {
    def unapply(str: String): Option[(String, String)] = {
        val parts = str split "\\."
        if (parts.length == 3){
            Some(parts(0), parts(2))
        }else{
            None
        }
    }
}

object Main extends App {
    "part1.somerandom.part2" match {
        case IgnoreBetween("part1", "part2") => println("matches")
        case _ => println("doesn't match")
    }
}

"Programming in Scala" and "Scala in depth" have amazing examples on pattern matching.

edited Oct 11, 2013 at 9:35

answered Oct 11, 2013 at 9:08

Eddie Jamsession

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Comments

maasg · Accepted Answer · 2013-10-11 10:23:45Z

0

We have created our custom matchers to deal with variable strings, basically using regex to express the expected outcome for a test. The cases where this is useful are plenty: A variable ID like in your case, different server URL's like when we run tests in QA lines, dates,...

What you want is some generic pattern matcher, something like:

def matches(expected : String, actual : String) = {
    val pattern = expected.r.pattern
    pattern.matcher(actual).matches
}

Example usage (on the REPL):

scala> matches("user id='(.+)' retrieved", "user id='12345' retrieved")
res1: Boolean = true

scala> matches("user id='(.+)' retrieved", "user id='12345' not found")
res2: Boolean = false

answered Oct 11, 2013 at 10:23

maasg

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1 Comment

maasg Over a year ago

We use cucumber for testing, and this resource is quite OK on simple regex usage for test purposes. It's cucumber related, but gives you a good idea on how to match expected inputs: richardlawrence.info/2010/07/20/…

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