Coverage not working with vitest

[bkeepers]

Describe the bug

Adding a CLI in openwatersio/neaps#182 and despite there being tests, the coverage report shows most of the command implementation is uncovered. I've tried both v8 and instanbul backends.

 % Coverage report from v8
-------------------------------------|---------|----------|---------|---------|-------------------
File                                 | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
-------------------------------------|---------|----------|---------|---------|-------------------
All files                            |   91.78 |     80.6 |   95.86 |   92.56 |
 cli/src                             |       0 |      100 |       0 |       0 |
  command.ts                         |       0 |      100 |       0 |       0 | 5-8
 cli/src/commands                    |      35 |     9.09 |   83.33 |   38.88 |
  extremes.ts                        |   47.61 |       20 |     100 |      50 | 69-83
  stations.ts                        |   21.05 |        0 |      50 |      25 | 32-52
 cli/src/formatters                  |   57.14 |        0 |      70 |   57.14 |
  index.ts                           |       0 |        0 |       0 |       0 | 6-31
  json.ts                            |      80 |      100 |   66.66 |      80 | 12
  text.ts                            |      80 |        0 |   83.33 |      80 | 23-27

To Reproduce

openwatersio/neaps#182 is a pretty minimal reproduction example.

Noteworthy:

• It's a monorepo, so had to set OCLIF_TEST_ROOT here.
• The app is using TypeScript, sourcemaps are being generated (tsconfig)

Expected behavior

Test coverage would accurately reflect what is covered. It's almost acting like the commands are loaded in process, but the actual command invocations are run in a fork/subprocess and the v8 instrumentation can't track it.

Environment (please complete the following information):

• OS & version: MacOS Tahoe and ubunto-latest (GitHub Actions)
• Shell/terminal & version: N/A
• node: 22.21.1 and 24.12.0
• typescript: 5.9.3
• vite: 4.0.17
• @oclif/core: 4.8.0
• @oclif/test: 4.1.15

Additional context

None

[bkeepers]

Is there a way to force @oclif/test to load the commands from src/ instead of the transpiled files in dist/?