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: util_test.go
    path of file: ./repos/echo/middleware
    
    the code of the file until where you have to start completion: // SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: Â© 2015 LabSta
    
func TestRandomStringBias(t *testing.T) {
	t.Parallel()
	const slen = 33
	const loop = 100000

	counts := make(map[rune]int)
	var count int64

	for i := 0; i < loop; i++ {
		s := randomString(slen)
		require.Equal(t, slen, len(s))
		for _, b := range s {
			counts[b]++
			count++
		}
	}

	require.Equal(t, randomStringCharsetLen, len(counts))

	avg := float64(count) / float64(len(counts))
	for k, n := range counts {
		diff := float64(n) / avg
		if diff < 0.95 || diff > 1.05 {
			t.Errorf("Bias on '%c': expected average %f, got %d", k, avg, n)
		}
	}
}