Test graphs

In order to support writing unit-tests, swh-graph provides three mechanisms, detailed in the sections below

Example dataset

Tests written in Python can use swh.graph.example_dataset.DATASET_DIR to get the path to the example dataset available locally.

They may also use fixtures from swh.graph.pytest_plugin such as graph_grpc_server_started to get the port of a temporary gRPC server process serving that graph, graph_grpc_stub to connect to that server as a gRPC client, or graph_client to get an HTTP client instance.

The example dataset/graph is static, and meant only to test common cases because any change to it breaks tests in swh-graph and dependent packages. To test more edge cases, you need to use one of the two methods below to generate your own graphs.

In-memory VecGraph

Tests written in Rust can use the GraphBuilder to define a graph with a high-level interface. The GraphBuilder returns a graph that implements the same traits as the real one.

JSON-serialized graph

An in-memory VecGraph can be serialized to JSON (or any format serde supports) using swh_graph::serde::serialize_with_labels_and_maps. For example, in JSON:

let file = std::fs::File::create(output_path)
    .with_context(|| format!("Could not create {}", output_path.display()))?;

let mut serializer = serde_json::Serializer::new(BufWriter::new(file));

swh_graph::serde::serialize_with_labels_and_maps(&mut serializer, &graph)
    .with_context(|| format!("Could not serialize to {}", output_path.display()))?;

These serialized graphs can then be loaded as a VecGraph again, using swh_graph::serde::deserialize_with_labels_and_maps. For example, in JSON:

let file = std::fs::File::open(&graph_path).with_context(|| {
    format!("Could not open {}", graph_path.display())
})?;

let mut deserializer =
    serde_json::Deserializer::from_reader(BufReader::new(file));

let graph = swh_graph::serde::deserialize_with_labels_and_maps(&mut deserializer)
    .map_err(|e| anyhow!("Could not read JSON graph: {e}"))?;

In particular, the gRPC server executable (swh-graph-grpc-serve) can read files serialized to JSON this way, using the --graph-format json option.

The JSON serialization, especially of properties, is not meant to be easily human-editable. Therefore, it is recommended to keep the Rust code used to generate it checked-in in your source code, and generate the JSON files at the beginning of your test suite (eg. as a session-scoped pytest fixture, for tests written in Python).