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Sunday, July 1, 2012

Using tags in SpecFlow features

Using tags in SpecFlow

While working with SpecFlow, I found that @Tags play the important role in running the tests in the mannered way.
@ignore is in other words the only tag that is supported by default and is translated to “IGNORE” in your test framework of choice (for example Ignore in NUnit or MsTest).
This can be used to disable features and/or scenarios that are not ready to be run yet.

Custom tags
You then have the liberty to make up any tag you want. For example Aslak Hellesoy list these;
@important @billing @bicker @annoy @qa_ready
You can also use tags for features and scenarios to refer to another system with requirements (TFS or JIRA for example) with the ID from that system. Love Aslak comment on that:

“if you have to deal with old school requirements in a different system”
Anyhow, in short – creativity is the limit. You can tag them with anything you want.

Using tags in SpecFlow hooks
But what for? What can I (or rather SpecFlow) do with them. There are two answers to my knowledge; hooks and test execution.

SpecFlow comes with a number of Hooks that in effect are events that is fired during the running of features and scenarios. SpecFlow can create a file with them all for you if you choose the SpecFlow Event Definition file template. The available hooks are and their running order are:


Luckily they are well-named so it’s easy to know when they run.
Also, they all take zero to more tags as an optional input that we can make use of to write specialized hooks. Like this:

public void BeforeScenario_testTag1()
So now you can write your own definitions on what’s going to happen when you tag a scenario (or feature) with a certain tag. Using this technique we have a @restoreDb that triggers a BeforeScenario-method with that tag ([BeforeScenario("restoreDb")] ) that does that, restore a new database in a virgin state for us.

Please note that you can use more than one tag in a Hook, like this:

[BeforeScenario("testTag1", "testTag2", "testTag3")]
public void BeforeScenario_testTags()

But then the tags are OR:ed together. So the above method (and the empty one) will be run for @testTag1, @testTag2 and @testTag3.

Feature: Tag demonstrator
                    In order to show the capabilities of tags in SpecFlow
                    As a developer
                    I want to write scenarios that has tags and show their usage in code

Scenario: Ignored scenario
                    Given that my scenario has the @ignore tag
                    When I run the scenario
                    Then the scenario is ignored
                    And the missing step definitions are not reported

Scenario: A scenario with 1 tag
                    Given that my scenario has 1 tags
                    When I run the scenario
                    Then before scenario hook with 'testTag1' is run
@testTag1 @testTag2 @testTag3
Scenario: A scenario with 3 tags
                    Given that my scenario has 3 tags
                    When I run the scenario
                    Then before scenario hook with 'testTag1, testTag2, testTag3' is run
@testTag1 @testTag3
Scenario: A scenario with 2 tags
                    Given that my scenario has 2 tags
                    When I run the scenario
                    Then before scenario hook with 'testTag1, testTag3' is run

Integration with test frameworks
But wait, there is more. If the test framework supports it (as NUnit and MsTest 4.0 does) the tags will be converted to Categories which you can use to run certain parts of your test suite.

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