I added a unit test. Ran into issues where adding the field would just send through a nil and had to add a time.Time conversion to metric.convertField.

That was the most time I've ever spent adding 9 lines of code.

So I don't know what to do about this failing check.

It's in plugins/inputs/ecs. They unmarshal the a json source file into a struct called ecsTask with a slice of ecsContainer structs in it. The ecsContainer struct has the CreatedAt and StartedAt fields, so that all makes sense. The final output function (metastats) creates a map with keys created_at and started_at with the values of CreatedAt and StartedAt, but the expected data does not have those fields.

Before changing the metric convert field function, the ecs metastats function didn't output the created_at and started_at keys, so the expected matched the output. I just don't know if that's actually supposed to be like that. It looks like a bug in the ecs test but I don't know much about ECS.

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