various tix improvements

.config/nextest.toml

@@ -3,5 +3,13 @@
 test-threads = 6
 fail-fast = false
 
+[[profile.default.overrides]]
+filter = 'test(status::monitor::tests::)'
+slow-timeout = { period = '30s', terminate-after = 4 }
+
+[[profile.default.overrides]]
+filter = 'package(gix-fsmonitor)'
+slow-timeout = { period = '30s', terminate-after = 4 }
+
 [profile.with-xml.junit]
 path = "junit.xml"

AGENTS.md

@@ -106,6 +106,25 @@ Follow "purposeful conventional commits" style:
 
 ### Test Best Practices
 
+- Tests must be isolated from the developer's checkout, other worktrees, shared
+  Git metadata, and user configuration. Use disposable repositories provided by
+  `gix-testtools`, such as `scripted_fixture_writable()`; never mutate a shared
+  read-only fixture or use the source checkout as a test repository.
+- Git invocations in test code must go through `gix_testtools::git()`,
+  `git_command()`, or fixture scripts executed by `gix-testtools`. Do not spawn
+  Git directly with `Command::new("git")` or ad hoc subprocess wrappers. If a test needs unsupported
+  command options, extend the shared isolated helper instead of bypassing it.
+  `run_git()` and `invoke_bash()` share this isolation. Subprocesses that invoke
+  Git indirectly must use `gix_testtools::configure_git_environment()` too.
+  Tests of APIs that read the process environment must use
+  `gix_testtools::run_in_isolated_process()` before exercising those APIs or
+  changing environment variables, so they cannot race other tests.
+- Setting a subprocess's working directory or passing `git -C` is not isolation:
+  inherited `GIT_DIR`, `GIT_WORK_TREE`, `GIT_COMMON_DIR`, `GIT_INDEX_FILE`, or
+  object-directory variables can redirect operations outside the fixture. Tests
+  that exercise such overrides must scope them to disposable test repositories.
+  Open repositories through the crate's isolated test helper or isolated `gix`
+  options, with only test-specific configuration overrides.
 - Run tests before making changes to understand existing issues
 - Use `GIX_TEST_IGNORE_ARCHIVES=1` when testing on macOS/Windows
 - Journey tests validate CLI behavior end-to-end