I find that the best way to set up test cases, regardless of language, is usually to use string constants in the proto text format (https://protobuf.dev/referen

I find that the best way to set up test cases, regardless of language, is usually to use string constants in the proto text format (https://protobuf.dev/reference/protobuf/textformat-spec/ https://protobuf.dev/reference/protobuf/textformat-spec/). For arrays, and especially for oneofs, it's way less verbose than how things are represented in Go, C++, or Java, and generally at least on par with the Python constructors. Maps are the only thing that suffer a bit, because they're represented as a list of key-val pairs (like in the wire format) instead of an actual map. Your language's compiler won't help you debug, but the parse-text-proto function can point to the source of the issue on a line/character level. With Go generics - and equivalent in most other languages - you can write a 5-line helper function that takes a string in that format and either returns a valid proto value (using the generic type param to decide which type to unmarshal) or `t.Fatal()`s. You would never do this in production code, but as a way to represent hand-written proto values it's pretty hard to beat.