Currently, there are at least two JS test files that test spilling to disk for the SBE HashAgg stage, i.e., jstests/aggregation/spill_to_disk.js and jstests/noPassthrough/spill_to_disk_secondary_read.js. However, none of these two files check the explain output regarding spilling to disk for the cases that involve an SBE HashAgg stage. To improve it, some assertions on the explain output is preferred, similar to how it's done for the HashLookup stage in SERVER-62676).

In addition, in jstests/aggregation/spill_to_disk.js, the setHashAggParameters function is not setting the parameters properly to support all test fixtures. For example, this test file is not even testing its intended scenario under the aggregation_one_shard_sharded_collections and aggregation_mongos_passthrough test suites. One possible solution is to use the FixtureHelpers.runCommandOnEachPrimary function, similar to how it's done in setHashLookupParameters (as part of SERVER-62676).