1. Create a function that returns the SharedPreferences instance:

fun getDefaultSharedPreferences() =                                 PreferenceManager.getDefaultSharedPreferences(InstrumentationRegistry.getContext())

2. Save a sample string to the SharedPreferences instance:

@Test
fun testUserParcelization() {
    val prefs = getDefaultSharedPreferences()
    val userName: String = "Gonzo"
    prefs.edit {
        putString("user_name", userName)
    }
}

3. Verify whether the string was successfully saved:

@Test
fun testSharedPrefs() {
    val prefs = getDefaultSharedPreferences()
    val userName: String = "Gonzo"
    prefs.edit {
        putString("user_name", userName)
    }

    val DEFAULT_VALUE = "empty"
    val fetchedUserName = prefs.getString("user_name",
     DEFAULT_VALUE)
    assertSame(userName, fetchedUserName)
}