If coverage information is available on your project, then the component viewer can help you visualize where combined test coverage is missing.
Coverage information is conveyed via color:
Coverage per tests
For Java projects using JaCoCo, it's possible to have "coverage per test" information. This includes:
Displaying the number of different tests that cover a specific line
Listing those tests
Being able to navigate to the test files that define those tests
These things are shown in a popup when you click on the coverage indicator. Clicking on a link in the popup window opens the test file in a pinned window.