You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: iterator_test.go
    path of file: ./repos/google-cloud-go/bigquery
    
    the code of the file until where you have to start completion: // Copyright 2015 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/L
    
func TestIteratorQueryID(t *testing.T) {
	testcases := []struct {
		description string
		src         *rowSource
		want        string
	}{
		{
			description: "nil source",
			src:         nil,
			want:        "",
		},
		{
			description: "empty source",
			src:         &rowSource{},
			want:        "",
		},
		{
			description: "populated id",
			src:         &rowSource{queryID: "foo"},
			want:        "foo",
		},
	}

	for _, tc := range testcases {
		// Don't pass a page func, we're not reading from the iterator.
		it := newRowIterator(context.Background(), tc.src, nil)
		got := it.QueryID()
		if got != tc.want {
			t.Errorf("%s: mismatch queryid, got %q want %q", tc.description, got, tc.want)
		}
	}
}