The test code for your component resides in a subfolder named __test__. Salesforce have embraced the open source framework known as Jest (https://jestjs.io/en/). Chapter 12, Unit Testing, will go into more detail on writing tests for Lightning Web Components. Finally, note that these tests are not uploaded to Salesforce and, thus, should be stored in your source control system and run locally as part of your build pipeline. This will also be covered in more detail in Chapter 13, Source Control and Continuous Integration.