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: s2a_test.go
    path of file: ./repos/google-cloud-go/auth/internal/transport
    
    the code of the file until where you have to start completion: // Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file exce
    
func TestGetS2AAddress(t *testing.T) {
	testCases := []struct {
		name   string
		respFn func() (string, error)
		want   string
	}{
		{
			name:   "test valid config",
			respFn: validConfigResp,
			want:   testS2AAddr,
		},
		{
			name:   "test error when getting config",
			respFn: errorConfigResp,
			want:   "",
		},
		{
			name:   "test invalid config",
			respFn: invalidConfigResp,
			want:   "",
		},
		{
			name:   "test invalid JSON response",
			respFn: invalidJSONResp,
			want:   "",
		},
	}

	oldHTTPGet := httpGetMetadataMTLSConfig
	oldExpiry := configExpiry
	configExpiry = time.Millisecond
	defer func() {
		httpGetMetadataMTLSConfig = oldHTTPGet
		configExpiry = oldExpiry
	}()
	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			httpGetMetadataMTLSConfig = tc.respFn
			if want, got := tc.want, GetS2AAddress(); got != want {
				t.Errorf("%s: want address [%s], got address [%s]", tc.name, want, got)
			}
			// Let the MTLS config expire at the end of each test case.
			time.Sleep(2 * time.Millisecond)
		})
	}
}