Do you do tests at 100%?

Should you do very thorough tests of every class, every type of enumeration? I have a enum in the project

public enum StorageDirectory {
/**
 * Directory for saving photos / pictures of movies
 */
IMAGE {
    @Override
    public String getGoogleDirectoryKey() {
        return "someKey1";
    }
},
/**
 * Directory for saving avatars of users
 */
AVATAR {
    @Override
    public String getGoogleDirectoryKey() {
        return "someKey2";
    }
};

/**
 * Get the directory key from the Google cloud.
 *
 * @return The key of the directory in the Google cloud
 */
public abstract String getGoogleDirectoryKey();
}

Should I do a test for this type of enumeration or do not overdo it with these tests?