Sharing State Between Step Definition Lessons – Grape Up
It’s an apparent reality for anybody who’s been utilizing Cucumber for Java in take a look at automation that steps have to be outlined inside a category. Passing take a look at state from one step definition to a different may be simply achieved utilizing occasion variables, however that solely works for elementary and small tasks. In any state of affairs the place writing cucumber eventualities is a part of a non-trivial software program supply endeavor, Dependency Injection (DI) is the popular (and normally needed!) resolution. After studying the article under, you’ll study why that’s the case and the best way to implement DI in your Cucumber-JVM checks shortly.
Preface
Let’s take a look on the following situation written in Gherkin:
If we assume that it’s a part of a small take a look at suite, then its implementation utilizing step definitions inside the Cucumber-JVM framework might appear to be this:
Within the instance above, the information is handed between step definitions (strategies) by way of occasion variables. This works as a result of the strategies are in the identical class – PurchaseProcess, since occasion variables are usually accessible solely inside the identical class that declares them.
Downside
The variety of step definitions grows when the variety of Cucumber eventualities grows. Eventually, this forces us to separate our steps into a number of lessons – to keep up code readability and maintainability, amongst different causes. Making use of this truism to the earlier instance would possibly end in one thing like this:
However now we face an issue: the checkPriceInHistory methodology moved into the newly created PurchaseHistory class can’t freely entry information saved in occasion variables of its unique PurchaseProcess class.
Resolution
So how will we go about fixing this pickle? The reply is Dependency Injection (DI) – the advisable means of sharing the state between steps in Cucumber-JVM.
In the event you’re unfamiliar with this idea, then go by Wikipedia’s definition:
“In software program engineering, dependency injection is a design sample during which an object or perform receives different objects or capabilities that it is dependent upon. A type of inversion of management, dependency injection goals to separate the considerations of establishing and utilizing objects, resulting in loosely coupled applications.[1][2][3] The sample ensures that an object or perform which needs to make use of a given service mustn’t must know the best way to assemble these providers. As an alternative, the receiving ‘shopper‘ (object or perform) is supplied with its dependencies by exterior code (an ‘injector’), which it’s not conscious of.” [1]
Within the context of Cucumber, to make use of dependency injection is to “inject a typical object in every class with steps. An object that’s recreated each time a brand new situation is executed.” [2]
Thus Comes PicoContainer
JVM implementation of Cucumber helps a number of DI modules: PicoContainer, Spring, Guice, OpenEJB, Weld, and Needle. PicoContainer is advisable in case your utility doesn’t already use one other one. [3]
The principle advantages of utilizing PicoContainer over different DI modules steam from it being tiny and easy:
- It doesn’t require any configuration
- It doesn’t require your lessons to make use of any APIs
- It solely has a single function – it instantiates objects [4]
Implementation
To make use of PicoContainer with Maven, add the next dependency to your pom.xml:
<dependency>
<groupId>io.cucumber</groupId>
<artifactId>cucumber-picocontainer</artifactId>
<model>7.8.1</model>
<scope>take a look at</scope>
</dependency>
If utilizing Gradle, add:
compile group: 'io.cucumber', identify: 'cucumber-picocontainer', model: ‚7.8.1’
To your construct.gradle file.
Now let’s return to our instance code. The implementation of DI utilizing PicoContainer is fairly simple. First, we have now to create a container class that can maintain the frequent information:
Then we have to add a constructor injection to implement the PurchaseProcess and PurchaseHistory lessons. This boils all the way down to the next:
- making a reference variable of the Container class within the present step lessons
- initializing the reference variable by way of a constructor
As soon as the adjustments above are utilized, the instance ought to appear to be this:
Conclusion
PicoContainer is light-weight and straightforward to implement. It additionally requires minimal adjustments to your present code, serving to to maintain it lean and readable. These qualities make it an ideal match for any Cucumber-JVM mission since sharing take a look at context between lessons is a query of ‘when’ and never ‘if’ in primarily any take a look at suite that can develop past a couple of eventualities.
