The boards have seldom applied the novelty test in their recent case law, but it was referred to in e.g. T 60/03 and T 1374/07, and is set out in Guidelines H-IV, 2.2 - June 2012 version. The beginning of point 1.7 also addresses the question of the validity of the novelty test.
T 133/85 (OJ 1988, 441) pointed out that care was necessary when applying the law relating to novelty to questions which arose in relation to Art. 123(2) EPC 1973. In T 177/86 the novelty test was described as "not very useful" for examining the admissibility of broadening a claim (see also T 150/07).
In T 201/83 (OJ 1984, 481) it was stated that the test for compliance with Art. 123(2) EPC 1973 was basically a novelty test, i.e. no new subject-matter may be generated by the amendment. This was approved in T 136/88. T 17/86 (OJ 1989, 297, Corr. 415) added that novelty could be found in a limitation, the addition to a claim of a further feature, or even in the absence of one of the elements of a device. The novelty test was incorporated in the Guidelines; reference is still made to this test in the June 2012 version (H-IV, 2.2), at least where the amendment is by way of addition (see also T 1374/07 quoting T 201/83).
In T 416/86 (OJ 1989, 309) it was held that the fact that a technical means (in this case an aperture of a special design) was known did not take away the novelty of its equivalents (in this case, apertures of a different design producing the same effect as the former) even if the equivalents were themselves well known. It followed that the equivalents of a disclosed technical means had to be considered new and therefore not disclosed if they were not mentioned in the original documents. In accordance with these principles, the board decided that the replacement of a specific feature disclosed in the invention by a broad general statement was to be considered as an inadmissible amendment under Art. 123(2) EPC 1973 when this general statement implicitly introduced for the first time specific features other than that originally disclosed. Therefore, the substitution in the claim of a structurally defined element of that claim by its known function (or disclosed function) was considered contrary to Art. 123(2) EPC 1973.
However, in T 873/94 (OJ 1997, 456) the board pointed out that where a proposal for amending an application involved the addition of a limiting feature to a claim, applying a "novelty test" was not appropriate for determining whether or not the amendment complied with Art. 123(2) EPC 1973. Following G 1/93 (OJ 1994, 541), the board pointed out that the underlying idea of Art. 123(2) EPC 1973 was clearly that an applicant should not be allowed to improve his position by adding subject-matter not disclosed in the application as filed, which would give him an unwarranted advantage and could be damaging to the legal security of third parties relying on the content of the original application. In the light of these considerations the addition to a claim before grant of an undisclosed limiting feature might or might not violate Art. 123(2) EPC 1973, depending on the circumstances.