Archive for the ‘Watir’ Category

How to write a ruby function that can accept either a string or a regular expression

July 30, 2008

While working on our unit test framework, I wanted to write a function that checks if a given Ext JS windoid is opened. The function should accept a title argument. This was easily implemented as:

	# title is a string with the exact windoid title
	def windoidDisplayed?(title)
		spans = $browser.spans
		t = $browser.length && $browser.detect {|i| \
			i.class_name == 'x-window-header-text' \
			&& title == i.text \
		}
		return t && t.visible?
	end

I then realized that users might not have the full title of the window, and might only want to check for a windoid with a title that matches some regular expression. A simple and naive way to do it is

	# title can be a string or a regular expression
	def windoidDisplayed?(title)
		spans = $browser.spans
		t = $browser.length && $browser.detect {|i| \
			i.class_name == 'x-window-header-text' \
				&& (title.kind_of?(String) \
					? (title == i.text) \
					: (title =~ i.text)) \
		}
		return t && t.visible?
	end

However, I didn’t want to check in every loop iteration if the passed title argument is regular expression. Although performance is really a non-issue in our unit tests, it just seemed to be a cumbersome and ugly code. I thought of using the dynamic nature of ruby to add a method (e.g. “match?”) to both string and regular expression classes, so I can call it in a polymorphic way without having to detect the type of title:

	class String
		def match?(x)
			return self == x
		end
	end
	
	class Regexp
		def match?(x)
			return self.match(x)
		end
	end
	
	# title can be a string or a regular expression
	def windoidDisplayed?(title)
		spans = $browser.spans
		t = $browser.length && $browser.detect {|i| \
				i.class_name == 'x-window-header-text' \
				&& title.match?(i.text) \
		}
	return t && t.visible?

Before implementing it, I thought I’d check if a similar function already exists in Ruby’s Standard Library, and indeed, when I looked up the Ruby book for functions that are in both String and Regexp classes, I run into “===” (the Case Equality operator), which is meant exactly for this kind of things. Unlike JavaScript, where the === operator is meant for identity, in Ruby, the === method is usually called in case expressions to match the case target for each when clause. As said in the documentation, for the String class, === method tests for equality and is the same as ==, but for Regexp class, === method tests for matches, and is the same as =~. Exactly what I was looking for. So my little function can simply be implemented like:

	# title can be a string or a regular expression
	def windoidDisplayed?(title)
		spans = $browser.spans
		t = $browser.length && $browser.detect {|i| \
				i.class_name == 'x-window-header-text' \
				&& title === i.text \
		}
		return t && t.visible?
	end

BTW, while searching for that, I took a look at Watir‘s sources, hoping to learn from the experts as I’m new to Ruby.
I found that Watir source (watir.rb, lines 50-70) does a similar trick to what I initially thought to do – define a new “matches” method (and not “match?” like the ruby convention that is also used in Watir in methods like “exists?” and “visible?“), and don’t use the === method.
In addition, in several places in the code there are still explicit tests for String class, such as the verify_contains method in input_elements.rb and navigate_to_link_with_id and navigate_to_link_with_url methods in watir_simple.rb.

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Handling browser on test start and end

July 23, 2008

When I started building a unit tests framework for our product, I decided that I want the browser to remain open through all tests, and only be closed at the end. This is because I don’t want a developer running these tests on his machine to be disturbed with many browser windows opened and closed.

However, as I quickly found out, there is no easy way to run code at the beginning and end of a test suite. This seems to be intentional, as each test case should be separate and independent of other tests in the suite. The setup and teardown methods are run for each test case.

One simple solution was to drop it and simply start the browser on every test case and close it on end, but when I played with it a little more, I reached an even better solution. I’m starting the browser at the beginning of the test and assign it to a global $browser. Then, if the test fail (which can be detected by @test_passed), we set $browser to nil, so the browser window remains, and subsequent tests create and use a new browser window. If the test succeed, the browser window is reused through $browser. At the end of the test, we close the browser if $browser is not nil. With this constellation, after the test suite finishes running, we have a browser open for each failed test, so we can inspect what went wrong and how the application looks at the time of the fail.

Here is the code I used to implement it:

# cleanup on close
END { # close browser at completion of the tests
$browser.close if $browser && $browser.exists? && !ENV[‘DONT_CLOSE_BROWSER_AT_END’]
Watir::IE.quit
}

module MyTestSuite < Watir::TestCase ############################################################# # setup method: # This setup function is called by the UnitTest framework before any test is run. # The function initialize the global $browser object if needed ############################################################# def setup return if $browser $browser = Watir::IE.new $browser.speed = :fast $browser.add_checker(PageCheckers::NAVIGATION_CHECKER) $browser.maximize unless ENV['DO_NOT_MAXIMIZE_BROWSER'] end ############################################################# # teardown method: # This teardown function is called by the UnitTest framework after any test is run. # The function reset the global $browser object in case an error # occurred (unless NO_NEW_BROWSER_ON_ERROR), so # a new browser window will be created in case an error occurred. ############################################################# def teardown $browser = nil unless @test_passed || ENV['NO_NEW_BROWSER_ON_ERROR'] end # ... test cases methods goes here end [/sourcecode]

Watir – first impressions

June 24, 2008

Our product doesn’t have unit tests. There, I said it. For a long time I’ve been looking for a way to build unit tests. There are three factors that prevented me to do so until now:

  1. It seems not to be really needed. When testing is needed, developers go over an installation and check that everything is working. Building a suite of tests to test all possible scenarios seems to be a huge task that doesn’t worth the effort.
  2. This is a web application that is constantly changing, so it seems hard to write robust test that will not break on every change. In addition, it uses a session ID that is passed in the URL, so URLs are different on every run.
  3. The data keeps changing. Our data is on the mainframe, and it is owned and used by other teams so we can’t expect to have the same data all the time, which makes it problematic to build solid tests.

In the past I tried using Selenium, but never really fell in love with it, and never got the time to deeply look into it and test it.
Recently I saw Ofer’s post about Watir and decided to take a better look at it and see if we can use it. Since I’m fluent at Javascript, and had a recent experience with Perl working on an installation automation project for a few months, catching Ruby was quite easy. As Ofer observed, Ruby seems to be a really nice language, but I have some problems adapting to Watir. For example, it took me sometime to understand how Javascript code can be invoked from Watir, but now I know it is done using:

$browser.ie.Document.parentWindow.execScript(js_expression)

At first, since I come from normal OO languages, I thought of creating a base ProductUnitTest class that derives from Watir::TestCase, and then, for each version or fix pack, we will create a VersionXXUnitTest class that will derive from ProductUnitTest. However, this doesn’t work well, since Test::Unit looks for all the included classes that derived from Test::Unit::TestCase, and since we would have to require ProductUnitTest in order to derived from it, Test::Unit will see two such class and will run the tests in ProductUnitTest twice – once for ProductUnitTest, and once for the derived VersionXXUnitTest.

Checking further, I came to the idea I have to use Ruby’s mixins, which is somewhat similar to Java’s interfaces, but more comfortable and easy to use, since Ruby is a dynamic language. So now, I define all basic tests and helper methods (like setup and teardown – see next post for more details on this) in a module named ProductUnitTest, and then, for each version, I define a VersionXXUnitTest class that derive from Watir::TestCase, and then includes ProductUnitTest so all the tests (and helper methods) are there, but only invoked once, for VersionXXUnitTest.

To conclude, Watir seems like a very nice framework to test our web application, and this will probably solve problem #2 above. I plan to broaden its use when we start building our next fix pack, where we have specific things we need to fix, and whenever we fix something, we should write a unit test for it right away. This is easier then writing and maintaining unit tests for an entirely new version that keeps changing. I hope that once our developers get used to it and see how it can help integration and acceptance tests they will see its value and overcome problem #1 above. I still need to find a good way to bypass problem #3.

I already showed what I did to Amit from QA, and she really liked it and said it might be useful for them as well.

P.S.
Another nice benefit of learning Ruby is that now I better understand some of the design made by the Prototype team members, which were clearly thinking in Ruby, as they are using Ruby on Rails.