Pact, ensure key names in array - arrays

Question

If returned json is a map, all key names specified in body response will be proved for existence. So
...
"response":
{
"status": 200,
"body":
{
"field1": "value1"
}
...
will ensure, that body contains a key "field1", if it is missing, an error occurs.
But what if response body is an array? I see no chance to test, if all or at least one element in this array have a specific key name. But this is important, I want to be warned if key names in backend are changing, because that would create errors in my application.

Answer 1

You can use eachLike to specify that array elements match a particular format. The correct syntax depends on which Pact framework you're using, but with pact-js, you would say:
const { somethingLike: like, term, eachLike } = pact
....
willRespondWith: {
status: 200,
body: eachLike({
"field1": "value1"
})
}
Here is the relevant part of the documentation.
Your example suggests you're writing the Pact file yourself - if this is the case, you can use the [*] notation to describe any array element, as described in the specification:
"response":
{
"status": 200,
"body":
[
{
"field1": "value1"
}
],
...
"matchingRules": {
"$.body": {
"min": 1,
"match": "type"
},
"$.body[*].field1": {
"match": "type"
},
...