[JUnit] Implement Cucumber as a Junit Platform Engine

[mpkorstanje]

Summary

Adds Cucumber implementation of JUnit Platforms TestEngine that will discover, filter and execute scenarios.

Fixes: #1149

Details

Motivation and Context

The motivation for this PR is two fold. To reduce the amount of configuration needed to run Cucumber and to facilitate developers of tooling that integrates Cucumber into test runners and IDE's.

Facilitating tooling

Unlike previous versions of JUnit, JUnit 5 is composed of several different modules from three different sub-projects.

JUnit 5 = JUnit Platform + JUnit Jupiter + JUnit Vintage

The JUnit Platform serves as a foundation for launching testing frameworks on the JVM. It also defines the TestEngine API for developing a testing framework that runs on the platform. By implementing Cucumber as a TestEngine we can benefit from existing implementations that use the JUnit Platform. This will make it easier to develop tooling for Cucumber - any tooling that supports the Junit Platform will automatically support the execution of Cucumber Scenarios. For example:

Note: Support is limited to running cucumber tests. Syntax highlighting, and other editor specific features are not supported.

Reduce boiler plate

In the ideal situation a project only contains step definitions and feature files. Currently however some additional setup is needed in the form of a runner class annotated with @CucumberOptions. By using the JUnit platform the presence of Cucumber on the class path will make it so that tooling can automatically execute features.

Coincidentally the JUnit Platform only allows a single source of configuration. This makes it clear in which configuration cucumber will be executed. This is an improvement over the current hierarchy of environment and annotation based variables.

How Has This Been Tested?

Work in progress

• Map ConfigurationParameters to RuntimeOptions in CucumberEngineExecutionContext. This will require some refactoring of RuntimeOptions. Note that not all options are valid in this context. Valid options are: --dry-run, --monochrome, --strict, --plugin and --glue.
• Document the available configuration parameters and how to use them in maven. Comparable to the documentation for Junit 5 itself.
• Resolve features suggested by ModuleSelector in DiscoverySelectorResolver
• Resolve features suggested by ClasspathRootSelector in DiscoverySelectorResolver
• Resolve features suggested by UniqueIdSelector in DiscoverySelectorResolver
• Resolve features suggested by UriSelector in DiscoverySelectorResolver.
• Implement getTags for PickleDescriptor, ScenarioOutlineDescriptor and FeatureFileDescriptor.
• Ensure IDEA picks up the CucumberTestEngine implementation. See: Add JUnit 5 Support #1149 (comment)
• Submit a patch Maven Surefire the JunitPlatformProvider to support non-class files. See: Add JUnit 5 Support #1149 (comment)

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).

Checklist:

• I've added tests for my code.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.