Patrick Xia a6daf411b9 minor: fix lint errors by using assert.Len
I noticed while prepping another PR that golangci-lint fails at HEAD.

Generated with

```perl -pi -e 's/assert[.]Equal[(]t, (\d+), len[(]([^)]+)[)][)]/assert.Len(t, $2, $1)/' gateway/gateway_test.go```
2023-10-22 17:44:15 -07:00
..
2023-04-05 23:39:15 +02:00