Cucumber Tests in Spring Boot with Dependency Injection

Cucumber Tests in Spring Boot with Dependency Injection

Cucumber is a great framework to create tests using a BDD approach. Unfortunately, the official website doesn’t provide too much documentation, so it might be tricky to set it up. In this post, I’ll show you how to combine Cucumber with Spring Boot using the cucumber-spring library to leverage Dependency Injection.

Table of Contents

The Spring Boot sample project

Updated (Feb 17th, 2021): This guide uses now Cucumber 6. If you want to check the changes needed to upgrade from Cucumber Spring version 4 to 6, have a look at the Pull Request

I’ll use a practical example to show you how to use Cucumber with Spring. If you want to check out the complete project’s source code, you can clone it from GitHub.

All the code in this post is available on GitHub: Spring Boot Cucumber. If you find it useful, please give it a star!

Let’s first define some minimum functionality: our web application will expose a REST API modeling a bag in which you can put different things via a REST API. Since Cucumber features are the best way to explain the functionality, let me just introduce the main feature we want to implement and test:

Feature: Bag functionalities

  Scenario: Putting one thing in the bag
    Given the bag is empty
    When I put 1 potato in the bag
    Then the bag should contain only 1 potato

  Scenario: Putting few things in the bag
    Given the bag is empty
    When I put 1 potato in the bag
    And I put 2 cucumber in the bag
    Then the bag should contain 1 potato
    And the bag should contain 2 cucumber
Important Note: This post does not cover Cucumber and Gherkin concepts. The good news is that there is another complete post on this same website doing that so, if you want to learn first how Cucumber and Gherkin work, just check it out.

You can use Cucumber to implement different types of tests. Normally, you use it to cover the ones on top of the test pyramid: integration or end-to-end tests. It’s the place where better fits the needs of mapping business language into feature testing, which usually crosses multiple modules (or components, or microservices…). While the other blog post in this site focuses on microservice end-to-end tests, this one draws the attention on intra-application Integration Tests, covering from the REST API all the way down (without mocks).

If you want to know more about the different ways of testing REST APIs (and Controllers) in Spring, you can also read the Guide to Testing Controllers with Spring Boot.

Required Libraries

We want to use Dependency Injection in our tests with Spring, so we’ll add the cucumber-spring dependency on top of the common cucumber-java and cucumber-junit, needed when you want to write Cucumber tests with Java and JUnit.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>io.tpd</groupId>
    <artifactId>spring-boot-cucumber</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spring-boot-cucumber</name>
    <description>Demo project using Cucumber DI and Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <cucumber.version>6.8.1</cucumber.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>io.cucumber</groupId>
            <artifactId>cucumber-java</artifactId>
            <version>${cucumber.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>io.cucumber</groupId>
            <artifactId>cucumber-junit</artifactId>
            <version>${cucumber.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>io.cucumber</groupId>
            <artifactId>cucumber-spring</artifactId>
            <version>${cucumber.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

As you see in the pom.xml file, this post has been updated to use Cucumber 6.8.

How Cucumber-Spring works

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Overview

The key part of this post: how to make DI work with Spring Boot? It’s simple but not really intuitive. Let’s see the steps.

Even though the sample application has only one controller, BagController, I split the tests into two different Cucumber Features in a way they also make use of two separate StepDefinition classes. This is to show you how to extract common Cucumber steps to a different class that may be shared by your other step-definition classes.

Spring Boot Cucumber Setup

Entry Point: @RunWith Cucumber

First, let’s have a simple class to configure each Cucumber test. This is just a shell that serves as an entry point for the test, together with its configuration. We’ll annotate it with @RunWith(Cucumber.class) to instruct JUnit to use this runner so we have all the Cucumber functionality.

All the code in this post is available on GitHub: Spring Boot Cucumber. If you find it useful, please give it a star!
package io.tpd.springbootcucumber.bagbasics;

import io.cucumber.junit.Cucumber;
import io.cucumber.junit.CucumberOptions;
import org.junit.runner.RunWith;

@RunWith(Cucumber.class)
@CucumberOptions(features = "src/test/resources/features/bagbasics",
        plugin = {"pretty", "html:target/cucumber/bagbasics"},
        extraGlue = "io.tpd.springbootcucumber.bagcommons")
public class BagCucumberIntegrationTest {
}

The @CucumberOptions annotation is responsible for pointing to the right feature package, configuring the plugin for a better reporting of tests both in the console output and as HTML, and specifying the package where extraGlue classes may be found. We use it to load configuration and classes that are shared between tests.

You might be wondering at this point how the Spring’s test context is loaded. That is indeed the trickiest part because that’s not configured in the integration test class. We’ll see that when we get there.

Note that, in this case, we have only one feature per Integration Test (the resource package referenced in the annotation only contains the bag.feature file). We could add more features within the same package and this example would still work.

Adding dependency injection to Cucumber tests

The piece of code that brings dependency injection to our Cucumber tests is the CucumberSpringConfiguration class. The @CucumberContextConfiguration annotation tells Cucumber to use this class as the test context configuration for Spring. In our case, we don’t need to change the configuration, nor we add extra beans here, but all that is possible within this class. Since we’re using Spring Boot, we can annotate this configuration class with @SpringBootTest. Note that this is confusing, since this class isn’t a test, but it’s just the convention that the Cucumber team decided to use. Check the Cucumber Spring README file on GitHub for more information and extra options.

package io.tpd.springbootcucumber.bagcommons;

import io.cucumber.spring.CucumberContextConfiguration;
import org.springframework.boot.test.context.SpringBootTest;

@CucumberContextConfiguration
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class CucumberSpringConfiguration {
}

A Test Component

Since we want to use the Spring context and dependency injection, let’s build a component to put that into practice. This class will abstract all the client’s API connections, so we don’t have to duplicate it within our Cucumber tests.

package io.tpd.springbootcucumber.bagcommons;

import io.tpd.springbootcucumber.Bag;
import org.springframework.boot.web.server.LocalServerPort;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;

import static io.cucumber.spring.CucumberTestContext.SCOPE_CUCUMBER_GLUE;

@Component
@Scope(SCOPE_CUCUMBER_GLUE)
public class BagHttpClient {

    private final String SERVER_URL = "http://localhost";
    private final String THINGS_ENDPOINT = "/things";

    @LocalServerPort
    private int port;
    private final RestTemplate restTemplate = new RestTemplate();

    private String thingsEndpoint() {
        return SERVER_URL + ":" + port + THINGS_ENDPOINT;
    }

    public int put(final String something) {
        return restTemplate.postForEntity(thingsEndpoint(), something, Void.class).getStatusCodeValue();
    }

    public Bag getContents() {
        return restTemplate.getForEntity(thingsEndpoint(), Bag.class).getBody();
    }

    public void clean() {
        restTemplate.delete(thingsEndpoint());
    }
}

As you see, this class is just providing common functionalities to our test. In this case, I created a RestTemplate and generic methods to use the application functionalities. The random port used by the test gets injected into the class as configured with the @LocalServerPort annotation.

The “cucumber-glue” scope tells Cucumber to remove this bean and recreate a new one if needed after each scenario. Here it’s just a way to keep everything clean but in some other cases might be very useful, e.g. if you alter context beans during a test.

The Step Definition classes

Injecting a component into a Cucumber step definition class

First, let’s have a look at the BagCucumberStepDefinitions class. It defines most of the steps needed in one of our Features, defined in the bag.feature file.

package io.tpd.springbootcucumber.bagbasics;

import io.cucumber.java.en.Then;
import io.cucumber.java.en.When;
import io.tpd.springbootcucumber.bagcommons.BagHttpClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;

import java.util.Collections;
import java.util.List;
import java.util.stream.IntStream;

import static org.assertj.core.api.Assertions.assertThat;

public class BagCucumberStepDefinitions {

    private final Logger log = LoggerFactory.getLogger(BagCucumberStepDefinitions.class);

    @Autowired
    private BagHttpClient bagHttpClient;

    @When("^I put (\\d+) (\\w+) in the bag$")
    public void i_put_something_in_the_bag(final int quantity, final String something) {
        IntStream.range(0, quantity)
                .peek(n -> log.info("Putting a {} in the bag, number {}", something, quantity))
                .map(ignore -> bagHttpClient.put(something))
                .forEach(statusCode -> assertThat(statusCode).isEqualTo(HttpStatus.CREATED.value()));
    }

    @Then("^the bag should contain only (\\d+) (\\w+)$")
    public void the_bag_should_contain_only_something(final int quantity, final String something) {
        assertNumberOfTimes(quantity, something, true);
    }

    @Then("^the bag should contain (\\d+) (\\w+)$")
    public void the_bag_should_contain_something(final int quantity, final String something) {
        assertNumberOfTimes(quantity, something, false);
    }

    private void assertNumberOfTimes(final int quantity, final String something, final boolean onlyThat) {
        final List<String> things = bagHttpClient.getContents().getThings();
        log.info("Expecting {} times {}. The bag contains {}", quantity, something, things);
        final int timesInList = Collections.frequency(things, something);
        assertThat(timesInList).isEqualTo(quantity);
        if (onlyThat) {
            assertThat(timesInList).isEqualTo(things.size());
        }
    }

}

Thanks to the dependency cucumber-spring and the class annotated with @CucumberContextConfiguration, Cucumber will load the Spring Boot context and will add the BagHttpClient component to it. In the step definitions classes, we can inject the beans using the Spring’s @Autowired annotation.

Keep in mind that your IDE might complain about this since this approach is a bit odd: @Autowired doesn’t normally work in classes that are not Spring beans. Again, this is just a convention that the Cucumber team decided to implement, which is a great improvement in comparison to how it used to work in previous Cucumber versions (if you’re curious, have a look at this post’s code for Cucumber 4 on GitHub).

Adding a second feature and shared steps

In a previous version of this post, some of you pointed out via comments that the proposed solution at that time wouldn’t work with more than one feature after upgrading Cucumber. The error was something like:

cucumber.runtime.CucumberException: Glue class XSteps and class YSteps both 
    attempt to configure the spring context.
Please ensure only one glue class configures the spring context.

The reason is that Cucumber 4 didn’t allow anymore to have two classes annotated with @SpringBootTest or extending a class with that annotation if they’re part of the same test. The solution at that time was to structure the test code a bit and use the extraGlue parameter whenever you want to use some extra classes.

The good news is that new versions of Cucumber have simplified how to work with Spring Boot and dependency injection in Cucumber tests. Now, we don’t need to do advanced tricks or annotate only one of the classes to make our test suite work. The Context Configuration has been extracted to a separate class, as we already covered.

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To make this case more representative, I created a second feature that makes use of some common steps. Both feature tests are configured by default to get all glue classes from within the same package so that parameter is omitted in my @CucumberOptions annotation. However, they both want to use the class BagCommonCucumberStepDefinitions located in a different package so that’s the reason for the extraGlue parameter.

@RunWith(Cucumber.class)
@CucumberOptions(features = "src/test/resources/features/bagextra",
        plugin = {"pretty", "html:target/cucumber/bagextra"},
        extraGlue = "io.tpd.springbootcucumber.bagcommons")
public class BagExtraCucumberIntegrationTest {
}

In Cucumber 4, you had to make sure that none of the classes in that package tried to load another Spring context via @SpringBootTest annotation. Now, this annotation is located at the context configuration class, making our life easier.

This is the class where we load the common step definition that we use in both features:

package io.tpd.springbootcucumber.bagcommons;

import io.cucumber.java.en.Given;
import org.springframework.beans.factory.annotation.Autowired;

import static org.assertj.core.api.Assertions.assertThat;

public class BagCommonCucumberStepDefinitions {

    @Autowired
    private BagHttpClient bagHttpClient;

    @Given("^the bag is empty$")
    public void the_bag_is_empty() {
        bagHttpClient.clean();
        assertThat(bagHttpClient.getContents().isEmpty()).isTrue();
    }

}

The HTTP client is injected via the @Autowired annotation, same as before.

Running the Application

You can now run the tests from your favorite IDE or using Maven:

$ mvn clean test

You’ll see how Cucumber prints the steps and the logs in between them:

...
Scenario: Putting one thing in the bag      # src/test/resources/features/bagbasics/bag.feature:3
  Given the bag is empty                    # io.tpd.springbootcucumber.bagcommons.BagCommonCucumberStepDefinitions.the_bag_is_empty()
2021-02-17 07:42:27.152  INFO 25870 --- [           main] i.t.s.b.BagCucumberStepDefinitions       : Putting a potato in the bag, number 1
  When I put 1 potato in the bag            # io.tpd.springbootcucumber.bagbasics.BagCucumberStepDefinitions.i_put_something_in_the_bag(int,java.lang.String)
2021-02-17 07:42:27.167  INFO 25870 --- [           main] i.t.s.b.BagCucumberStepDefinitions       : Expecting 1 times potato. The bag contains [potato]
  Then the bag should contain only 1 potato # io.tpd.springbootcucumber.bagbasics.BagCucumberStepDefinitions.the_bag_should_contain_only_something(int,java.lang.String)
...
Scenario: Putting few things in the bag # src/test/resources/features/bagbasics/bag.feature:8
  Given the bag is empty                # io.tpd.springbootcucumber.bagcommons.BagCommonCucumberStepDefinitions.the_bag_is_empty()
2021-02-17 07:42:27.194  INFO 25870 --- [           main] i.t.s.b.BagCucumberStepDefinitions       : Putting a potato in the bag, number 1
  When I put 1 potato in the bag        # io.tpd.springbootcucumber.bagbasics.BagCucumberStepDefinitions.i_put_something_in_the_bag(int,java.lang.String)
2021-02-17 07:42:27.201  INFO 25870 --- [           main] i.t.s.b.BagCucumberStepDefinitions       : Putting a cucumber in the bag, number 2
2021-02-17 07:42:27.205  INFO 25870 --- [           main] i.t.s.b.BagCucumberStepDefinitions       : Putting a cucumber in the bag, number 2
  And I put 2 cucumber in the bag       # io.tpd.springbootcucumber.bagbasics.BagCucumberStepDefinitions.i_put_something_in_the_bag(int,java.lang.String)
2021-02-17 07:42:27.213  INFO 25870 --- [           main] i.t.s.b.BagCucumberStepDefinitions       : Expecting 1 times potato. The bag contains [potato, cucumber, cucumber]
  Then the bag should contain 1 potato  # io.tpd.springbootcucumber.bagbasics.BagCucumberStepDefinitions.the_bag_should_contain_something(int,java.lang.String)
2021-02-17 07:42:27.216  INFO 25870 --- [           main] i.t.s.b.BagCucumberStepDefinitions       : Expecting 2 times cucumber. The bag contains [potato, cucumber, cucumber]
  And the bag should contain 2 cucumber # io.tpd.springbootcucumber.bagbasics.BagCucumberStepDefinitions.the_bag_should_contain_something(int,java.lang.String)

That will only happen if you set the plugin “pretty” in @CucumberOptions (like we did in this example). Since we also set the option to generate HTML reports, we’ll have them available in the target/cucumber folder. Don’t expect fancy reports, it’s very simple - yet functional.

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About Moisés Macero

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