On latest central, I have the following snapshot failure when running the debugger tests:

Summary of all failing tests
FAIL packages/devtools-reps/src/object-inspector/tests/component/window.js
  ● ObjectInspector - dimTopLevelWindow › renders window as expected when dimTopLevelWindow is true

    expect(value).toMatchSnapshot()

    Received value does not match stored snapshot "ObjectInspector - dimTopLevelWindow renders window as expected when dimTopLevelWindow is true 2".

    - Snapshot
    + Received

    @@ -57,11 +57,11 @@
          onClick={[Function]}
          onKeyDownCapture={null}
          role="treeitem"
        >
          <span
    -       className="tree-indent"
    +       className="tree-indent tree-last-indent"
          >
            ​
          </span>
          <div
            className="node object-node lessen"

      43 |     nodes = wrapper.find(".node");
      44 |     expect(nodes.at(0).hasClass("lessen")).toBeFalsy();
    > 45 |     expect(wrapper).toMatchSnapshot();
         |                     ^
      46 |   });
      47 | 
      48 |   it("renders collapsed top-level window when dimTopLevelWindow =false", () => {

      at Object.<anonymous> (object-inspector/tests/component/window.js:45:21)
      at step (object-inspector/tests/component/window.js:3:191)
      at object-inspector/tests/component/window.js:3:361

(and 3 others but removed them from here, they look the same). You can also find them on this recent try run: https://taskcluster-artifacts.net/dEwXsDpbSYm8ftVj2LLVSA/0/public/logs/live_backing.log

It should lead to Jest failing, but it doesn't. The test ends with jestPassed: true,

I suspect the devtools node test suite has the same issue.

ni? Jason: we probably need a better error detection logic for Jest. Any idea?

I believe that david recently fixed these source tree jest issues. With that said, I'm really not sure how the runner is failing. It gives and exit code 1 locally. I'm looking into it though.

I'm really not sure how the runner is failing.

If you refer the log from try, it failed on flow, so it's not directly related. Sorry if it was confusing.
The point is that Jest is failing, but the runner is not failing.

https://hg.mozilla.org/mozilla-central/rev/e62a90a57da1