Unable to mock fetchQuery in Relay for testing

**Title**: Unable to mock fetchQuery in Relay for testing

**Issue description:**

I am currently working on a Relay project and I need to test a component that uses `fetchQuery` to execute a query. However, I am unable to find a straightforward way to mock the response for fetchQuery. I am aware of the `relay-test-utils` package and its `createMockEnvironment` function, but I am not sure how to apply it specifically for `fetchQuery`.

Here's an example of the code I am testing:

```
export const getLocationName = (
LocationFilter: LocationQuery$variables
) => {
return new Promise((resolve) => {
fetchQuery(
RelayEnvironment,
LocationQuery,
LocationFilter,
{ fetchPolicy: "network-only" }
).subscribe({
next: (data) => {
if (data.eLocation?.edges) {
resolve(convertData(data.Location.edges));
}
resolve([]);
},
});
});
};
```
I have tried using createMockEnvironment and tried various approaches to mock the response of `fetchQuery`, but I have not been successful.

Could you please guide me on how to properly mock the response of `fetchQuery` for testing purposes? Any help or pointers would be greatly appreciated.

Thank you.