Gherkin - simply re-use Given statements as When statements... acceptable?

Question

Here are three example BDD statements that should help explain my question:

Scenario: User logs in
Given I am on the login screen
When I enter the valid username "myUsername"
And I enter the valid password "myPassword"
And I press the login button
Then I should see the login successful page

Scenario: User buys a product
Given I am logged into the system using username "myUsername" and "myPassword"
When I purchase the product "myProduct"
Then I should have "myProduct" in the product inventory

vs

Scenario: User buys a product
Given I am on the login screen
And I enter the valid username "myUsername"
And I enter the valid password "myPassword"
And I press the login button
When I purchase the product "myProduct"
Then I should have "myProduct" in the product inventory

So scenario 1 above is fine, but which is best out of statement 2 and 3. Statement 2 reads nicely and more concisely. But my step definition for "Given I am logged into the system using username "myUsername" and "myPassword"" will need to repeat calls to the Page Objects (or equivalent) that scenario 1 called... seems like more dev effort.

So really just wondering if anyone knows which is best practise. I have searched online and found the following document: http://docs.behat.org/guides/1.gherkin.html

This suggestions scenario 2 is best, but then writes: "Authenticate a user (An exception to the no-interaction recommendation. Things that “happened earlier” are ok)" which kinda lends itself to scenario 3.

Cheers,

Charlie

Answer 1

Here is my review of the scenarios you've written.

Scenario 1

Scenario: User logs in
Given I am on the login screen
When I enter the valid username "myUsername"
And I enter the valid password "myPassword"
And I press the login button
Then I should see the login successful page

Pros : You are correctly using the Given, When and Then statements. In this scenario the Given sets the initial state of the system, the When indicates actions which a user will take and the Then details the assertions made to verify the behaviour of the system.

Cons : Whilst what you have written will work, the problem you have is that this test is brittle. If your company was to mandate that a time-dependent security token also had to be specified during log-in (for example), you'd have to add another step to input this additional field. However if you rewrote this step to be declarative e.g.

Given I am on the login screen
When I submit valid log-in criteria
Then I should see the login successful page

Then if the log-in process was changed, you would only need to alter the code, the scenario would remain the same.

Scenario 2

Scenario: User buys a product
Given I am logged into the system using username "myUsername" and "myPassword"
When I purchase the product "myProduct"
Then I should have "myProduct" in the product inventory

Pros : Same as above.

Cons : Again the test is brittle as it's imperative i.e. you are specifying the exact log-in credentials and a specific product. I'd re-write this as:

Given I am logged into the system
When I purchase a product
Then I should have that product in the product inventory

You can save the product specified in the "When" step in ScenarioContext.Current. You would then be able to re-use this value in your "Then" step to assert that it is present in the product inventory.

Scenario 3

Scenario: User buys a product
Given I am on the login screen
And I enter the valid username "myUsername"
And I enter the valid password "myPassword"
And I press the login button
When I purchase the product "myProduct"
Then I should have "myProduct" in the product inventory

Cons : This is the worst of your scenarios as you are incorrectly using the Given statement. A Given statement should be used to define an initial system state for the test, so in this case "Given I am on the login screen" is a correct use, but "Given I enter the valid username "myUsername"" is an incorrect use. It is incorrect as it is indicating a user action, hence it should be covered by a When. Yes, you can use a Given to perform the same programmatic steps as a When, but it doesn't make it right!

I'd change this scenario to the version I suggested in Scenario 2.