Add --agent flag to test runners for low-noise output

.claude/rules/testing/overview.md

@@ -9,24 +9,19 @@ Quarto's test suite lives in `tests/`. For comprehensive documentation, see `tes
 
 ## Running Tests
 
+Use `--agent` — collapses a green run to a dot per test plus a tally line; failures keep assertion message, source frame, stack, exit code.
+
 ```bash
 cd tests
 
 # Linux/macOS
-./run-tests.sh                              # All tests
-./run-tests.sh smoke/render/render.test.ts  # Specific test
-./run-tests.sh docs/smoke-all/path/test.qmd # Smoke-all document
+QUARTO_TESTS_NO_CONFIG="true" ./run-tests.sh --agent unit/my-test.test.ts
 
 # Windows (PowerShell 7+)
-.\run-tests.ps1
-.\run-tests.ps1 smoke/render/render.test.ts
+$env:QUARTO_TESTS_NO_CONFIG="true"; .\run-tests.ps1 --agent unit/my-test.test.ts
 ```
 
-**Skip dependency configuration:**
-```bash
-QUARTO_TESTS_NO_CONFIG="true" ./run-tests.sh test.ts    # Linux/macOS
-$env:QUARTO_TESTS_NO_CONFIG=$true; .\run-tests.ps1      # Windows
-```
+Plain form (no `--agent`), full flag list, rerun-on-failure workflow, bash-only reporter-collision caveat: `tests/README.md`.
 
 ## Test Types
 

.claude/rules/testing/smoke-all-tests.md

@@ -22,6 +22,8 @@ Document-based tests using YAML metadata for verification. Tests live in `tests/
 .\run-tests.ps1 docs/smoke-all/path/to/test.qmd
 ```
 
+Add `--agent` for low-noise output — see `.claude/rules/testing/overview.md` § Running Tests.
+
 ## Test Structure
 
 Tests are defined in `_quarto.tests` YAML metadata:

.claude/rules/testing/typescript-tests.md

@@ -20,6 +20,8 @@ TypeScript-based tests using Deno. Smoke tests render documents; unit tests veri
 .\run-tests.ps1 smoke/render/render.test.ts
 ```
 
+Add `--agent` for low-noise output — see `.claude/rules/testing/overview.md` § Running Tests.
+
 ## Core Infrastructure
 
 Core test files (`test.ts`, `verify.ts`, `utils.ts`) are described in `.claude/rules/testing/overview.md` § Core Files.

tests/README.md

@@ -224,6 +224,29 @@ $env:QUARTO_TEST_KEEP_OUTPUTS="true"
 ./run-tests.ps1
 ```
 
+**--agent flag**
+- Switches deno's reporter to `--reporter=dot`, collapsing a green run's output to roughly two bytes per test plus deno's tally line
+- Failures keep what identifies them: assertion message, source frame, stack, exit code, and the harness-assembled rerun command (see below) all survive
+- What's dropped is captured console output (progress prints outside the assertion message), for every test, passing or failing - a few places rely on that as their only diagnostic, notably a snapshot mismatch, whose unified diff is printed rather than thrown (the `.diff` file is still written to disk)
+- Explicit opt-in only - no environment or TTY detection, so a human and an agent running the same command see the same output unless this flag is passed
+- Not a general "quiet" flag: deno's own `-q`/`--quiet` is never forwarded (it's a no-op under `--reporter=dot`)
+
+```bash
+./run-tests.sh --agent unit/my-test.test.ts
+```
+
+```powershell
+./run-tests.ps1 --agent unit/my-test.test.ts
+```
+
+*Recovering from a failure under `--agent`:* the failure message the harness prints already contains a ready-to-run rerun command for most test failures (tests registered through `unitTest`/`testQuartoCmd`, failing inside the render/verify step). A few cases don't get that assembled command and need a fallback:
+- A **smoke-all** document failure: the printed command reruns the whole `smoke-all.test.ts` corpus rather than just the failing document - use the document path shown in the test name instead.
+- A few files register directly with `Deno.test` rather than through the harness (`smoke/create/create.test.ts`, `smoke/logging/log-level-and-formats.test.ts`, `integration/playwright-tests.test.ts`) - for these the reported source location is the actual test file, but deno prints it as `path/to/file.test.ts:line:column`; strip the `:line:column` suffix before passing it back to the runner, since the runner's file-type check only accepts a path ending in `.ts`/`.qmd`/`.md`/`.ipynb` and rejects the location as printed.
+- For anything else (a setup/teardown failure, or any failure that isn't Error-shaped), rerun the original command with `--agent` removed - this always works and needs no output parsing.
+- Do **not** use the location in the `FAILURES` summary section as a rerun target for harness-registered tests - it resolves to `test.ts`'s own `Deno.test` call site, which registers no tests of its own and would rerun nothing.
+
+*Reporter collision (bash only):* passing `--agent` together with a reporter already set via `QUARTO_DENO_EXTRA_OPTIONS` is unsupported - deno rejects duplicate `--reporter` arguments and exits non-zero. This combination is not detected or blocked by the wrapper; it surfaces as a deno error. (On PowerShell this combination cannot occur: `QUARTO_DENO_EXTRA_OPTIONS` isn't currently honored there at all.)
+
 **Other environment variables**
 - `QUARTO_TEST_VERBOSE` - Enable verbose test output
 - `QUARTO_TESTS_NO_CHECK` - Not currently used (legacy variable)