@Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        MessageSubject that = (MessageSubject) obj;
        return Objects.equals(this.value, that.value);
    }
@Test
    public void testEquals() {
        new EqualsTester()
                .addEqualityGroup(subject1, sameAsSubject1)
                .addEqualityGroup(subject2)
                .addEqualityGroup(subject3)
                .testEquals();
    }