Fixed flaky tests resulting from getDeclaredFields method used in a dependency. This causes the order of the fields returned by preparedOperation to be non-deterministic.

[Auzel]

This PR fixes the flaky tests that results when preparedOperation.get() is compared to an expected query string, say for example, "SELECT " + ALL_FIELDS + " FROM " + TABLE + " WHERE " + TABLE + ".first_name = $1". The assumption is that preparedOperation.get() returns the field names in the exact order ALL_FIELDS is declared with. However, this is not the case. To be more specific, the the field names returned by preparedOperation.get() can be in any of the n! orders, where n is the number of fields querying for. This non-deterministic behavior is due to the getDeclaredFields() method called in one of your dependencies (org.springframework.util.ReflectionUtils). And as specified by the javaDocs for getDeclaredFields(), The elements in the returned array are not sorted and are not in any particular order.

My fix is to sort the fields for both the expected and actual query strings prior to checking whether they are equal. I, however, excluded applying this fix to cases where only one field was queried because 1!=1, and so those tests are deterministic.

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[nt-gt]

A few code suggestions from a drive-by reviewer (not a member, so the remarks might not be relevant).

[nt-gt]

Suggested change

	for(String sortedField: sortedFieldsList){
	if(sortedFieldsList.get(0)!=sortedField){
	sortedFields.append(", ");
	}
	sortedFields.append(sortedField);
	}
	return sortedFields.toString();
	return String.join(", ", sortedFields);

[schauder]

Thanks for bringing this up.
I polished and merged this and also ported it to 3.0.x which lives in spring/projects/spring-data-relational now.