• fundamental: fundamental column types
• multiset: std::multiset with all [Split]Index{32,64} column types
• optional: std::optional with different element types
• pair: std::pair with different element types
• set: std::set with all [Split]Index{32,64} column types
• string: std::string with all [Split]Index{32,64} column types
• tuple: std::tuple with different element types
• unique_ptr: std::unique_ptr with different element types
• unordered_multiset: std::unordered_multiset with all [Split]Index{32,64} column types
• unordered_set: std::unordered_set with all [Split]Index{32,64} column types
• variant: std::variant with Switch column type
• vector: std::vector with all [Split]Index{32,64} column types

In the RNTuple Validation Suite, we cannot test all possible nesting combinations of supported types. Furthermore, we assume that the column encoding on disk is orthogonal to the nesting of fields. We therefore cover a strategic selection based on field structural roles that is described below. Implementations should exercise specific details related to nesting of types in their own unit tests. In particular, this includes any optimization that contradicts the assumptions made above.

For leaf fields, we test all possible column encodings in a top-level field.

For collection fields (for example std::vector), we want to test all [Split]Index{32,64} column types.

If C is a container type with a single item field, we test the following nestings:

• C<std::int32_t>
• C<C<std::int32_t>>

If M is an dictionary container type, we test the following nestings:

• M<std::int32_t, std::int32_t>
• M<M<std::int32_t, std::int32_t>, M<std::int32_t, std::int32_t>>

For record fields of type R (for example std::tuple), we want to test nesting with other field structural roles:

• Leaf fields of types std::int32_t and std::string (the latter is particular because it has variable length and two columns)
• Variant field of type std::variant<std::int32_t, std::string>
• Collection field of type std::vector<std::int32_t>
• Record field of the type R itself

In addition, we test the nesting of the record type inside a collection field, std::vector<R>.

As there is only one type that results in this field structural role, the reader is referred to the variant directory.