jsTestLog("Running initial query on the oplog");                                                                                                                                                                                                                              
{
    const res = assert.commandWorked(localDb.runCommand({
        find: "oplog.rs",
        filter: {op: "i", "o.ans": 42},
        hint: {$natural: 1}, 
        batchSize: 1,
        $_requestResumeToken: true
    }));

    assert.eq(res.cursor.firstBatch.length, 1, res);
    assert.eq(res.cursor.firstBatch[0].o._id, 0, res);

    // Assert resume token is non-null.
    const resumeToken1 = assertExpectedResumeTokenFormat(res); // <-- fails

[js_test:resume_after_against_oplog] uncaught exception: Error: Not all of the values from [ "postBatchResumeToken" ] were in {
[js_test:resume_after_against_oplog]    "firstBatch" : [
[js_test:resume_after_against_oplog]            {
[js_test:resume_after_against_oplog]                    "op" : "i",
[js_test:resume_after_against_oplog]                    "ns" : "test.resume_after_against_oplog",
[js_test:resume_after_against_oplog]                    "ui" : UUID("5efe291d-440f-4726-bd19-328987fca64b"),
[js_test:resume_after_against_oplog]                    "o" : {
[js_test:resume_after_against_oplog]                            "_id" : 0,
[js_test:resume_after_against_oplog]                            "ans" : 42
[js_test:resume_after_against_oplog]                    },
[js_test:resume_after_against_oplog]                    "ts" : Timestamp(1617146515, 17),
[js_test:resume_after_against_oplog]                    "t" : NumberLong(1),
[js_test:resume_after_against_oplog]                    "wall" : ISODate("2021-03-30T23:21:55.763Z"),
[js_test:resume_after_against_oplog]                    "v" : NumberLong(2)
[js_test:resume_after_against_oplog]            }
[js_test:resume_after_against_oplog]    ],
[js_test:resume_after_against_oplog]    "id" : NumberLong("895888238858507122"),
[js_test:resume_after_against_oplog]    "ns" : "local.oplog.rs"
[js_test:resume_after_against_oplog] } :
[js_test:resume_after_against_oplog] doassert@src/mongo/shell/assert.js:20:14
[js_test:resume_after_against_oplog] assert.hasFields@src/mongo/shell/assert.js:286:13
[js_test:resume_after_against_oplog] assertExpectedResumeTokenFormat@jstests/replsets/resume_after_against_oplog.js:32:5
[js_test:resume_after_against_oplog] @jstests/replsets/resume_after_against_oplog.js:54:26
[js_test:resume_after_against_oplog] @jstests/replsets/resume_after_against_oplog.js:8:2
[js_test:resume_after_against_oplog] failed to load: jstests/replsets/resume_after_against_oplog.js
[js_test:resume_after_against_oplog] exiting with code -3