findStringInDetails = (id, contents) => {
    let t = async_test(`auto-expand on find-in-page match: ${id}`);
    document.body.insertAdjacentHTML("beforeend", `<details id=${id}>${contents}</details>`);
    let details = document.getElementById(id);
    details.ontoggle = t.step_func_done(function(e) {
        details.remove();
        assert_equals(e.newState, "open", `newState is “open”: ${id}`);
        assert_equals(e.oldState, "closed", `oldState was “closed”: ${id}`);
        assert_true(details.open, `details element is open: ${id}`);
    });
    testRunner.findInPage(id, []);
}
let target;
target = "details-simple"; findStringInDetails(target, target);
target = "details-in-p"; findStringInDetails(target, `<p>${target}</p>`);
target = "details-in-table"; findStringInDetails(target, `<table><tr><td>${target}</table>`);
target = "details-nested-simple"; findStringInDetails(target, `<details>${target}</details>`);
target = "details-nested-target-in-p"; findStringInDetails(target, `<details><p>${target}</p></details>`);
target = "details-nested-target-in-table"; findStringInDetails(target, `<details><table><tr><td>${target}</table></details>`);

findStringInDetails = (id, contents) => {
    let t = async_test(`auto-expand on find-in-page match: ${id}`);
    document.body.insertAdjacentHTML("beforeend", `<details id=${id}>${contents}</details>`);
    let details = document.getElementById(id);
    details.ontoggle = t.step_func_done(function(e) {
        details.remove();
        assert_equals(e.newState, "open", `newState is “open”: ${id}`);
        assert_equals(e.oldState, "closed", `oldState was “closed”: ${id}`);
        assert_true(details.open, `details element is open: ${id}`);
    });
    testRunner.findInPage(id, []);
}
let target;
target = "details-simple"; findStringInDetails(target, target);
target = "details-in-p"; findStringInDetails(target, `<p>${target}</p>`);
target = "details-in-table"; findStringInDetails(target, `<table><tr><td>${target}</table>`);
target = "details-nested-simple"; findStringInDetails(target, `<details>${target}</details>`);
target = "details-nested-target-in-p"; findStringInDetails(target, `<details><p>${target}</p></details>`);
target = "details-nested-target-in-table"; findStringInDetails(target, `<details><table><tr><td>${target}</table></details>`);

(you’ll need to scroll to see the full script)

findStringInDetails = (id, contents) => {
    let t = async_test(`auto-expand on find-in-page match: ${id}`);
    document.body.insertAdjacentHTML("beforeend", `<details id=${id}>${contents}</details>`);
    let details = document.getElementById(id);
    details.ontoggle = t.step_func_done(function(e) {
        details.remove();
        assert_equals(e.newState, "open", `newState is “open”: ${id}`);
        assert_equals(e.oldState, "closed", `oldState was “closed”: ${id}`);
        assert_true(details.open, `details element is open: ${id}`);
    });
    testRunner.findInPage(id, []);
}
let target;
target = "details-simple"; findStringInDetails(target, target);
target = "details-in-p"; findStringInDetails(target, `<p>${target}</p>`);
target = "details-in-table"; findStringInDetails(target, `<table><tr><td>${target}</table>`);
target = "details-nested-simple"; findStringInDetails(target, `<details>${target}</details>`);
target = "details-nested-target-in-p"; findStringInDetails(target, `<details><p>${target}</p></details>`);
target = "details-nested-target-in-table"; findStringInDetails(target, `<details><table><tr><td>${target}</table></details>`);

(you’ll need to scroll to see the full script — 19 lines)

The Test Metadata page's section for implementation-status states that the set of values permitted are:

One of the values implementing, not-implementing or default.

Looking back through chat here, it seems that the backlog is a Mozilla-specific addition (and I presume unsupported was renamed to not-implementing). So, my guess is that the full set of values permitted for Mozilla's testing metadata is:

• implementing: Something that is going to be implemented fully in an agent, but perhaps not yet?
• not-implementing: Something that an agent does not intend to implement, usually in agent-specific metadata.
• default: Something that is fully implemented in an agent.
• backlog: Things that Firefox intends to ship…eventually.

• Is the above set of values and their definitions correct?

• Assuming the above, why is implementing used as the default, and not default? Is default an outdated status, maybe?

So I think that the command line parsing is the only bit that actually validates the implementation-status values.

I also think you're correct that the docs are wrong to claim there's a "default" value; that should be "implementing", and "backlog" is missing.

Okay, so, the actual set of values seems to be:

• implementing: Anywhere from "is being implemented" to "we believe we have fully implemented this" for an agent; the intent is "yes please let's test this".
• not-implementing: Agent is not planning on implementing this, please don't test it.
• backlog: Seems like this shouldn't be Firefox-specific. Basically, it means, "we intend to implement this, but plz don't test it like implementing yet".

☝🏻 Sound fair?

jgraham: Okay, so, the actual set of values seems to be:

• implementing: Anywhere from "is being implemented" to "we believe we have fully implemented this" for an agent; the intent is "yes please let's test this".
• not-implementing: Agent is not planning on implementing this, please don't test it.
• backlog: Seems like this shouldn't be Firefox-specific. Basically, it means, "we intend to implement this, but plz don't test it like implementing yet".

☝🏻 Sound fair?