Cucumber: You're not allowed to extend classes that define step definitions or hooks

Question

I have inherited from others a big project of testing whose main Java classes are CommonSteps, CommonBase and CommonScript. They are currently related in this way:

CommonSteps extends CommonBase

CommonBase extends CommonScript

The problem is with the next method when I try to run the project with mvn clean install:

@After
public void tearDown(Scenario scenario) {
  if (scenario.isFailed()) {
    // Take a screenshot...
    final byte[] screenshot = ((TakesScreenshot) driver).getScreenshotAs(OutputType.BYTES);
    scenario.embed(screenshot, "image/png"); // ... and embed it in the report.
  }
}

I get the error:

cucumber.runtime.CucumberException: You're not allowed to extend classes that define step definitions or hooks: steps.CommonSteps extends class common.CommonBase.

How could I start working with dependency injection deleting everything related to inheritance?

Answer 1

Cucumber creates a new instance of all classes defining stepdefs before each scenario. It then invokes stepdef methods on one of those instances whenever it needs to run a step.

If you defined a stepdef method foo in class A and you have a class B extends A you'd get an a and b instance. The foo method would be available on both instances, and Cucumber would not be able to decide what instance to invoke the method on.

That's why we don't allow it.

The solution is to use composition instead of inheritance. You can achieve composition with dependency injection - Cucumber supports several popular DI frameworks.