if opts.initialCluster == "" {
		def := fmt.Sprintf(initialClusterFmt, opts.name, opts.peerPort)
		opts.initialCluster = fallbackToEnvWithDefault("initial-cluster", initialClusterEnv, def)
	}

	if opts.peerListenUrls == "" {
		def := fmt.Sprintf(peerListenUrlsFmt, opts.peerPort)
		opts.peerListenUrls = fallbackToEnvWithDefault("listen-peer-urls", peerListenUrlsEnv, def)
	}

	if opts.peerAdvertiseUrls == "" {

			expectedValue: "foo",
		},
	}

	for _, test := range testCases {
		t.Run(test.desc, func(t *testing.T) {
			setEnvVar(t, test.env, test.value, test.valueSet)
			value := fallbackToEnvWithDefault("some-flag", test.env, test.defaultValue)
			if value != test.expectedValue {
				t.Errorf("unexpected result: %s, expected: %s", value, test.expectedValue)
			}
		})
	}