What's a good approach to unit test an NSDateFormatter? [duplicate] - swift

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Convert string with unknown format (any format) to date
(2 answers)
Closed 6 years ago.
I have an array of dates that I would like to get an NSDate object from, using an NSDateFormatter.
let dates = [
"Tue, 04 Feb 2014 22:03:45 Z",
"Sun, 05 Jun 2016 08:35:14 Z",
"Sun, 05 Jun 2016 08:54 +0000",
"Mon, 21 Mar 2016 13:31:23 GMT",
"Sat, 04 Jun 2016 16:26:37 EDT",
"Sat, 04 Jun 2016 11:55:28 PDT",
"Sun, 5 Jun 2016 01:51:07 -0700",
"Sun, 5 Jun 2016 01:30:30 -0700",
"Thu, 02 June 2016 14:43:37 GMT",
"Sun, 5 Jun 2016 01:49:56 -0700",
"Fri, 27 May 2016 14:32:19 -0400",
"Sun, 05 Jun 2016 01:45:00 -0700",
"Sun, 05 Jun 2016 08:32:03 +0000",
"Sat, 04 Jun 2016 22:33:02 +0000",
"Sun, 05 Jun 2016 01:52:30 -0700",
"Thu, 02 Jun 2016 15:24:37 +0000"
]
I was going with the GWT pattern, but felt strange structuring my unit test like that, because I need to write a dozen or more distinct test funtions for each case.
Can anyone suggest a better approach to this? Or is this an acceptable usage of the "Given, When, Then" pattern?
..I really don't want to have a testRFC822DateFormatter1(), testRFC822DateFormatter2(), testRFC822DateFormatter3(),...
func testRFC822DateFormatter() {
// Given
let rfc822DateFormatter = RFC822DateFormatter()
let dateString = "Tue, 04 Feb 2014 22:03:45 Z"
// When
let date = rfc822DateFormatter.dateFromString(dateString)
// Then
XCTAssertNotNil(date)
let components = NSCalendar.currentCalendar().components([.Year, .Month, .Day, .Hour, .Minute, .Second, .TimeZone, .Calendar], fromDate: date!)
XCTAssertEqual(components.day, 4)
XCTAssertEqual(components.month, 2)
XCTAssertEqual(components.year, 2014)
XCTAssertEqual(components.hour, 22)
XCTAssertEqual(components.minute, 3)
XCTAssertEqual(components.second, 45)
XCTAssertEqual(components.timeZone?.daylightSavingTimeOffset, 3600)
XCTAssertEqual(components.timeZone?.secondsFromGMT, 3600)
XCTAssertEqual(components.calendar?.calendarIdentifier, NSCalendarIdentifierGregorian)
}
Thank you!

Answer 1

There are two kinds of tests you need.
1) A test to ensure that a particular dateFormat works properly with a particular format of date.
2) A test to ensure that if two different dateFormats work on a particular format of date, that they are either both the same or your logic will pick the correct one.
So I would envision one test for each dateFormat and one test for each date that could potentially match more than one format.
For these tests, the GWT pattern is fine as far as I can tell. It's more a matter of identifying all the various date formats you will need to use and making sure that the correct date format is used for each date.
As an aside, I wouldn't be comfortable subclassing NSDateFormatter, nor do I see that it's necessary... For the inputs you specify in your question, the code below is all that's necessary:
let dateFormatter1: NSDateFormatter = {
let result = NSDateFormatter()
result.dateFormat = "EEE, d MMM yyyy HH:mm:ss Z"
return result
}()
let dateFormatter2: NSDateFormatter = {
let result = NSDateFormatter()
result.dateFormat = "EEE, d MMM yyyy HH:mm Z"
return result
}()
let dateFormatter3: NSDateFormatter = {
let result = NSDateFormatter()
result.dateFormat = "EEE, d MMM yyyy HH:mm:ss z"
return result
}()
func dateFromString(dateString: String) -> NSDate? {
return dateFormatter1.dateFromString(dateString) ?? dateFormatter2.dateFromString(dateString) ?? dateFormatter3.dateFromString(dateString)
}
And for the code above, I would expect a total of three tests, one for each date formatter.