todo

Handle IO (& other) errors in cleanup helper

next

artifact directory; use adjustoption in the testcase builders, with an extra argument for the directory name, to describe a hierarchy for saving test artifacts (stdout, logs, screenshots) and also getting mocked input (stdin, reference screenshots, etc). con: need to specify both directory name and human readable test name. will need a type for directory names; use overloadedstrings and throw an error if it has bad chars. don't clobber old artifact directories; put each in a separate dir with e.g. timestamp in the name provide an option for building the directory structure without running the tests. This has the advantage of giving a standardized structure to test artifacts for review. will need an option for the root artifact directory. e.g.
```
root_artifact_dir
+> run_1970_01_01_00_00_00
|  +> test_artifact_hierarchy
|
+> run_1970_01_01_01_00_00
   +> test_artifact_hierarchy
```

someday

Chromedriver compatibility: several tests are ignored for chromedriver due to spec-noncompliance. Some of these can be fixed -- notably the findElement tests -- by figuring out how to interpret chromedriver's responses.
/session/{session id}/element/{element id}/displayed
Need a ci test matrix, but have to think about how to prevent combinatorial blowup; dependencies are geckodriver+firefox+chromedriver+chrome, so matrix will get big fast. Compromise: only support one version of the drivers at a time?

Notes on ignored tests

getAlertText on headless geckodriver https://bugzilla.mozilla.org/show_bug.cgi?id=1460857