if err != nil {
		t.Error(err)
	} else if s := string(b); !strings.HasPrefix(s, "User-agent:") {
		t.Errorf("Incorrect page body (did not begin with User-agent): %q", s)
	}
}

func TestClientHead(t *testing.T) { run(t, testClientHead) }
func testClientHead(t *testing.T, mode testMode) {
	cst := newClientServerTest(t, mode, robotsTxtHandler)
	r, err := cst.c.Head(cst.ts.URL)
	if err != nil {
		t.Fatal(err)
	}