It’s an apparent truth for anybody who’s been utilizing Cucumber for Java in take a look at automation that steps should be outlined inside a category. Passing take a look at state from one step definition to a different might be simply achieved utilizing occasion variables, however that solely works for elementary and small initiatives. In any scenario the place writing cucumber eventualities is a part of a non-trivial software program supply endeavor, Dependency Injection (DI) is the popular (and normally obligatory!) resolution. After studying the article beneath, you’ll be taught why that’s the case and the right way to implement DI in your Cucumber-JVM assessments shortly.
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 occasion variables. This works as a result of the strategies are in the identical class – PurchaseProcess, since occasion variables are typically accessible solely inside the identical class that declares them.
The variety of step definitions grows when the variety of Cucumber eventualities grows. In the end, 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 may lead to one thing like this:
However now we face an issue: the checkPriceInHistory technique moved into the newly created PurchaseHistory class can’t freely entry information saved in occasion variables of its unique PurchaseProcess class.
So how can we go about fixing this pickle? The reply is Dependency Injection (DI) – the beneficial manner of sharing the state between steps in Cucumber-JVM.
If you happen to’re unfamiliar with this idea, then go by Wikipedia’s definition:
“In software engineering, dependency injection is a design pattern during which an object or function receives different objects or capabilities that it will depend on. A type of inversion of control, dependency injection goals to separate the concerns of setting up and utilizing objects, resulting in loosely coupled packages. The sample ensures that an object or operate which desires to make use of a given service shouldn’t need to know the right way to assemble these providers. As a substitute, the receiving ‘client‘ (object or operate) is supplied with its dependencies by exterior code (an ‘injector’), which it’s not conscious of.” 
Within the context of Cucumber, to make use of dependency injection is to “inject a standard object in every class with steps. An object that’s recreated each time a brand new situation is executed.” 
Thus Comes PicoContainer
JVM implementation of Cucumber helps a number of DI modules: PicoContainer, Spring, Guice, OpenEJB, Weld, and Needle. PicoContainer is beneficial in case your utility doesn’t already use one other one. 
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 characteristic – it instantiates objects 
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 easy. First, now we have to create a container class that can maintain the widespread information:
Then we have to add a constructor injection to implement the PurchaseProcess and PurchaseHistory lessons. This boils right down to the next:
- making a reference variable of the Container class within the present step lessons
- initializing the reference variable by a constructor
As soon as the adjustments above are utilized, the instance ought to appear to be this:
PicoContainer is light-weight and simple to implement. It additionally requires minimal adjustments to your current 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 number of eventualities.