Why does the testing library use pointer instead of value receivers?

[red_888]

Been reading about when to use a pointer or value receiver and I think I know most of the reasons for making the decision but, now I’m curious about this specific example:

// Example of using the testing library
func TestHelloName(t *testing.T) {
	name := "Gladys"
	want := regexp.MustCompile(`\b` + name + `\b`)
	msg, err := Hello("Gladys")
	if !want.MatchString(msg) || err != nil {
		t.Fatalf(`Hello("Gladys") = %q, %v, want match for %#q, nil`, msg, err, want)
	}
}

I would LOVE to know the reason pointer receivers were chosen for the testing library- I think this would be helpful for my understanding. Did they chose a pointer because large structs could be passed to it? Or is there something inherent to how the testing library is used that makes pointer receivers the right choice here?

[NobbZ (Norbert Melzer)]

Because it contains fields it mutates fur some calls. Most prominent is probably the muted it holds.

[red_888]

Why does it have to mutate some variables for certain methods? just want to understand the whole use case better

[NobbZ (Norbert Melzer)]

Mutexes are usually used to avoid writing from many go routines to the same memory address and therefore producing races.

Also, as from a test function noting is returned, but instead methods of the test “objects” are called, it has to keep the results stored in itself.