The content of a PDF document can be arranged in multiple layers. Section 8.11.2.1 of the PDF specification “PDF 32000-1:2008” says: “An optional content group is a dictionary representing a collection of graphics that can be made visible or invisible dynamically by users of conforming readers.”.

Adobe Reader® uses the term “Layer” and the specification uses the term “OCG”. They are equivalent.

PDFUnit provides the following tags to test layers:

<!-- Tags to test layers: -->

<!-- 
  'Layer' means the same as 'OCG, Optional Content Group'. 
  So they have the same type:
-->

<hasNumberOfLayers />, <hasNumberOfOCGs />

<!-- Nested tags: -->
<hasLayer> or <hasOCG>
  <withName>                 (required)
    <matchingComplete />     (one of these nested tags ...
    <containing       />     ...
    <startingWith     />     ... is required)
  </withName>
</hasLayer> or </hasOCG>

<hasLayers> or <hasOCGs>
  <allWithoutDuplicateNames />  (optional)
</hasLayers> or </hasOCGs>

The tag <endingWith /> is not provided because duplicate layer names are expanded internally with a suffix and thus the end of a name is not predictable.

A tag matchingRegex /> is also not provided because layer names are usually short.

The first tests check the number of existing layers (OCGs):

<testcase name="hasNumberOfOCGs">
  <assertThat testDocument="layer/hang-man-game.pdf">
    <hasNumberOfOCGs>40</hasNumberOfOCGs>     
    <hasNumberOfLayers>40</hasNumberOfLayers> 
  </assertThat>
</testcase>

The next example tests the name of a layer:

<testcase name="hasLayerWithName_MatchingComplete">
  <assertThat testDocument="layer/simpleLayerDemo.pdf">
    <hasLayer>
      <withName>
        <matchingComplete>Parent Layer</matchingComplete>
      </withName>
    </hasLayer>
  </assertThat>
</testcase>

The tags endingWith /> and matchingRegex /> are intentionally not provided as explained at the beginning of this chapter.

String comparisons are case-insensitive. Whitespaces remain unchanged.

<!-- Layer names are treated case-insensitive. -->

<testcase name="hasLayerWithName_CaseInSensitive">
  <assertThat testDocument="layer/simpleLayerDemo.pdf">
    <hasLayer>
      <withName>
        <matchingComplete>parent layer</matchingComplete>
      </withName>
    </hasLayer>
    <hasLayer>
      <withName>
        <matchingComplete>Parent Layer</matchingComplete>
      </withName>
    </hasLayer>
  </assertThat>
</testcase>

PDFUnit provides a tag to verify that a document has no duplicate layer names:

<testcase name="hasLayers_AllWithoutDuplicateNames">
  <assertThat testDocument="layer/simpleLayerDemo.pdf">
    <hasLayers>
      <allWithoutDuplicateNames />
    </hasLayers>
    <hasOCGs>                   <!-- <hasOCGs /> is equal to <hasLayers /> -->
      <allWithoutDuplicateNames />
    </hasOCGs>
  </assertThat>
</testcase>

In the current release 2015.10 PDFUnit does not provide functions to verify the content of a single layer.