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One of the frameworks used in BDD context is Cucumber, which Xray has prime support for.  In this context, you may want to have a look at a BDD tutorial provided by the Cucumber team tutorial for Java.

Similarly to what happens with other frameworks, with Cucumber "specification" and "implementation" are two distinct things, even though related: the test specification is done in natural language using Gherkin, while the implementation of each specification's phrase (i.e., step) is done in code (e.g., Java, Ruby or some other language).

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1. Create Cucumber tests (e.g., Scenario/Scenario Outlines) and their respective step code in some other tool.
2. Import existing Cucumber tests using the REST API (e.g., from an existing code base which may have tests, and their corresponding step implementation) 
3. Optionally, and in parallel, 
   1. Specify additional or edit existing Cucumber tests in natural language, in Jira.
   2. Implement remaining tests in code and commit them to the source code versioning system.
4. Export Cucumber features from Jira to the CI environment, using the REST API or the Jenkins/Bamboo plugins.
5. Execute tests in the CI environment.
6. Report results to Xray, using the REST API or the Jenkins/Bamboo plugins.
7. Repeat from step 3 onwards.

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Common problems

Submission of Cucumber results says "No tests found in execution result"

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