Scalar types

Path: TestServer / DataTypes / Scalar (RW) and Scalar/ReadOnly (read-only siblings).

21 variables per group, one per OPC UA built-in scalar type.

Read-write scalars

Values come from src/TestServer/AddressSpace/DataTypesBuilder.cs. Boundary-value tests should use your own data — the initial set is deliberately mild so that round-trip tests have a known neutral starting point.

All RW: write the new value, read it back, expect equality.

Read-only scalars

Path: TestServer / DataTypes / ReadOnly

Same 21 types as above, suffixed _RO. accessLevel = CurrentRead. Writes return Bad_NotWritable.

Test patterns

Round-trip every type

For each RW variable:

write(<node>, <new-value>)
assert read(<node>) == <new-value>

Covers wire encoding + decoding for the full type set.

Read-only rejection

For each RO variable:

status = write(<node>, <some-value>)
assert status == Bad_NotWritable

Type-specific notes

• Int64 / UInt64 — make sure your library doesn't downcast to 32-bit. The initial values are well within 32-bit range, but try writing 2^63 or 2^64 - 1 to verify.
• ByteString — opaque bytes, not a UTF-8 string. Some libraries silently convert; test with bytes that aren't valid UTF-8 (e.g., 0xff, 0xfe).
• Guid — standard XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX format. Endian handling differs between libraries; test with a non-symmetric GUID.
• DateTime — OPC UA uses 100-nanosecond ticks from epoch 1601-01-01 UTC. Many libraries convert to native datetime types; verify sub-second precision survives.
• StatusCode — a UInt32 wrapping a status. Don't accidentally treat it as a number — your client should expose it as a StatusCode type with helpers.
• LocalizedText — { locale, text } pair. Some servers store only text; the suite stores both.
• QualifiedName — { namespaceIndex, name }. The namespace index in the value is independent of the namespace of the variable holding it.
• NodeId / ExpandedNodeId — when written, the server doesn't validate that the NodeId points anywhere real. They're raw values.

Why exhaustive coverage matters

A client that reads/writes Int32 correctly but mishandles UInt64 will fail on real PLCs that use both. This 21-variable sweep is the cheapest test for "did we wire all the encoders".

For a single client-side test that fans across all 21:

for type, node in scalars:
    write(node, sample_value_for(type))
    assert read(node).value == sample_value_for(type)

Sample values are your call. Boundary values (Int16.MAX, UInt32.MAX, empty string, DateTime.MinValue) flush out overflow bugs your library may have.

Where to read next

• Arrays and matrices — array variants of these types plus 2D/3D matrices.
• Testing patterns · Basic tests — recipes for round-trip tests.