BDD in Java with Cucumber


Reusing steps

I wanted to re-use some BDD steps by using inheritance:

import io.cucumber.java.en.Then;
import static javax.ws.rs.core.Response.Status.CREATED;
import static javax.ws.rs.core.Response.Status.NO_CONTENT;
import static javax.ws.rs.core.Response.Status.fromStatusCode;

public class CommonSteps {
  @Then("the changes SHOULD be saved.")
  public void the_changes_SHOULD_be_saved() throws Exception {
    Response.Status status = fromStatusCode(mSaveResponse.statusCode());
    assertTrue(CREATED == status || NO_CONTENT == status);
  }
}

And then extending CommonSteps in my feature test class:

public class BoxingFeatureTest extends CommonSteps {
}

Would be nice, right?

Well, turns out Cucumber was having none of it:

[ERROR] com.example.app.RunCucumberTestIT  Time elapsed: 0.397 s  <<< ERROR!

cucumber.runtime.CucumberException: You're not allowed to extend
classes that define Step Definitions or hooks. class
com.example.app.BoxingFeatureTest extends class
com.example.app.CommonSteps

The trick is to have a state class that holds all the values you need to share between the different classes implementing the BDD steps:

public class StepValues() {
  private HttpResponse<String> saveResponse;
  public void setSaveresponse(final HttpResponse<String> pResponse) {
    saveResponse = pResponse;
  }
  public HttpResponse<String> getSaveResponse() {
    return saveResponse;
  }
}

In the classes where you implement steps, you then inject an instance of this value object:

public class CommonSteps() {
  public CommonSteps(final StepValues pState) {
    state = pState;
  }
public class MoreSteps() {
  public MoreSteps(final StepValues pState) {
    state = pState;
  }

When running this with Cucumber, Cucumber will inject an instance of StepValues into CommonSteps and MoreSteps. That is, if you have cucumber-picocontainer on your classpath, otherwise you're given this helpful error message:

cucumber.runtime.CucumberException: class
com.example.app.SomeSteps
doesn't have an empty constructor. If you need DI, put
cucumber-picocontainer on the classpath

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