}

		if string(b) != tt.s {
			t.Errorf("slice changed to %s; want %s", b, tt.s)
		}
		if len(tt.a) > 0 {
			if want := tt.a[len(tt.a)-1] + "z"; string(x) != want {
				t.Errorf("last appended result was %s; want %s", x, want)
			}
		}
	}
}

// Test case for any function which accepts and returns a byte slice.
// For ease of creation, we write the input byte slice as a string.
type StringTest struct {