I figured this out while writing the question, but figured it might be useful to someone :)
I had code processing JSON from a callout, and it all worked fine, but when I put the exact same JSON in my mock, SF throws an error trying to parse it. I have validated the JSON and it is exactly what I receive in the actual callout.
The error says System.JSONException: Unexpected character ('n' (code 110)): was expecting comma to separate ARRAY entries at [line:1, column:232]
The 'n' is the first letter of 'name' in the JSON at column 232 here: ...state.completion", "[{\"name\":\"connect_adapt...
and the full string is below. Removing the escape quotes did not change anything, but clearly it seems related to them somehow.
{
"columns":[
{
"name":"chef_node_id"
},
{
"name":"serverHost"
},
{
"name":"metric_name"
},
{
"name":"checklist"
}
],
"warnings":[
],
"values":[
[
"node-fvyhpgt2",
"node-fvyhpgt2_coupa_software_3",
"getting_started.state.completion",
"[{\"name\":\"connect_adapters\",\"completed\":true}, {\"name\":\"examine_device\",\"completed\":true}, {\"name\":\"query_saved\",\"completed\":true}, {\"name\":\"device_tag\",\"completed\":false}, {\"name\":\"enforcement_executed\",\"completed\":false}, {\"name\":\"dashboard_created\",\"completed\":true}, {\"name\":\"report_generated\",\"completed\":true}]"
]
],
"matchingEvents":0.0,
"status":"success",
"omittedEvents":0.0
}
