Why isn't Xcode showing test coverage?

Question

Using Xcode 8.2.1

A suite of Swift XCT unit tests isn't highlighting code coverage (with green/red highlighting and numbering) on the corresponding swift file when run.

• I have ticked code coverage : Gather coverage data in the test scheme.
• I have tried deleting ~/Library/Developer/Xcode/DerivedData and
  ~/Library/com.apple.dt.Xcode, in finder.
• I have tried quitting simulator and running again.
• I have tried running all tests with cmd ⌘ + U, the diamond in the test class, and individual tests.
• All tests are passing

I know the report navigator can show coverage but it is in a detached way.

Answer 1

Works fine on my machine:

Don't forget to choose Editor > Show Code Coverage (you didn't mention that in your little checklist).