const data = [
    id: 1,
    plan_name: foo,
    description: foo bar,
    test: [
           id: 44,
           activity_name: bar,
           comment: var
          ],
    userId: 3
];

{{#each data}}
    <p>{{plan_name}}</p>>
    <p>{{test}}</p>
{{/each}}

p1

>
[object Object],[object Object]

p2

>
[object Object],[object Object],[object Object]

p3

>
[object Object],[object Object]