Testing

cargo test                      # everything
cargo test --lib                # unit tests only (60)
cargo test --test integration   # integration tests only (11)
cargo test tracker::            # one module
cargo test -- --nocapture       # see printed output

71 tests in total. They run in a few seconds and need no API key, no network and no Steam installation.

The no-network rule

No test may contact the public internet. The strategies used instead:

Concern	Strategy
Steam JSON	Literal payload strings in unit tests, recorded fixtures in integration tests
HTTP client	Only construction is tested; the request path is covered by testing its inputs (URLs) and outputs (parsers) separately
A2S protocol	A real UdpSocket bound to 127.0.0.1, answering with crafted packets
Filesystem	Unique paths under std::env::temp_dir(), cleaned up afterwards
Clock	Timestamps are passed in as plain strings ("T0", "T1", …)

Unit tests

src/config.rs — 11 tests

Covers defaults, the two required keys, environment overrides and every error path: defaults_are_sane, minimal_config_loads_with_defaults, explicit_values_override_defaults, missing_api_key_is_error, missing_steam_id_is_error, nonexistent_file_is_error, invalid_toml_is_error, api_key_env_override, steam_id_env_override, env_can_supply_missing_keys, example_config_parses_and_has_required_keys.

Environment-touching tests share a static ENV_LOCK: Mutex<()> because std::env::set_var is process-global.

src/tracker.rs — 10 tests

One per transition plus the edge cases: empty_tracker_starts_idle, start, running, switch, end, resume, closed_last_entry_not_resumed, apply_meta, apply_meta_out_of_bounds, into_log_returns_underlying.

These are the tests to read first — they are the executable specification of the session lifecycle.

src/steam/api.rs — 10 tests

Type projection (summary_without_game_is_none, summary_to_current_game_maps_fields, summary_missing_game_extra_info_uses_app_name), parsing (parse_player_summaries_maps_in_game_and_idle_players, parse_player_summaries_empty_players, parse_player_summaries_garbage_is_error, parse_player_summaries_skips_row_with_bad_steamid, parse_friends_filters_non_friends), URL construction (url_builders_produce_expected_urls) and JSON round-tripping (entry_to_json_round_trips).

src/a2s.rs — 9 tests

Pure parser tests (parses_standard_response, parses_goldsrc_response, rejects_garbage, handles_utf8_names_lossy) plus five that run a loopback UDP server in a background thread: round_trip_with_echo_server, query_without_port_uses_default, challenge_round_trip, challenge_repeat_gives_up, query_unreachable_port_errors.

:::warning query_without_port_uses_default binds port 27015 It must, because it verifies the default-port behaviour — so the test fails if something else on the machine (a real game server, another test run) already holds UDP 27015. :::

src/storage.rs — 8 tests

missing_file_reads_empty, round_trip_preserves_entry, pretty_output_with_skipped_optionals, overwrite_replaces_old_log, no_stray_temp_file_after_write, malformed_json_is_error, bare_array_is_normalized, nested_parent_dir_created.

Paths are made unique with an AtomicU32 counter plus the process id, so parallel test threads never collide.

src/enrich.rs — 6 tests

no_friends_plays_nothing, same_game_friends_filters_sorts_dedupes, lobby_friends_matches_same_lobby, lobby_friends_ignored_when_no_lobby, no_gameserver_ip_yields_no_server_or_map, build_assembles_enrichment.

src/steam/client.rs — 6 tests

client_constructs plus exhaustive coverage of the 100-id chunking: chunks_empty, chunks_under_limit, chunks_exact_limit, chunks_over_limit, chunks_preserve_order.

Integration tests — 11 tests

tests/integration.rs uses only the public API, exactly as an external crate would.

Test	Covers
config_load_roundtrip	Config defaults through the public API
config_missing_required_key_errors	Error surface from outside the crate
parse_player_summaries_fixture	A realistic 3-player payload
summary_to_current_game_fixture	Fixture row → CurrentGame
parse_friends_fixture	Friend list parsing
enrich_same_lobby_from_fixture	Both matchers over the same fixture
tracker_end_to_end	start → running → meta → switch → end
tracker_resume_closes_open_session	Restart mid-session
log_json_shape	Exact JSON key sets for full and minimal entries
storage_roundtrip_temp	Write → read with every field populated
steamlog_sample_fixture_parses	The documented sample log stays valid

Fixtures

File	Shape	Used by
tests/fixtures/player_summaries.json	Full GetPlayerSummaries response: the tracked user in TF2 with a lobby and server, a friend in the same lobby, a friend in CS2	3 integration tests
tests/fixtures/friends.json	GetFriendList response with two friends	parse_friends_fixture
tests/fixtures/steamlog_sample.json	A log with one closed, fully enriched session and one open session	steamlog_sample_fixture_parses, and the examples in these docs

The fixtures contain the complete Steam payload shape — avatars, clan ids, timestamps — not just the fields SteamLogger reads, which is what proves the #[serde(default)] tolerance works.

Writing a new test

• Put unit tests in the module's own #[cfg(test)] mod tests, integration tests in tests/integration.rs.
• Build temp paths with the existing unique_path/test_path helpers; never write into the repository.
• Pass timestamps as short literals ("T0"), not real dates, unless the test is about formatting.
• If a test needs an environment variable, lock ENV_LOCK first.
• Assert on error substrings (err.contains("api_key")), not on exact messages — the anyhow context chain may grow.

Continuous integration

The repository has no Rust CI workflow yet; the documentation site is built and deployed by .github/workflows/docs.yml. A minimal Rust job would be:

.github/workflows/rust.yml (suggested)

name: rust
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@stable
        with:
          components: clippy, rustfmt
      - run: cargo fmt --check
      - run: cargo clippy --all-targets -- -D warnings
      - run: cargo test

Note the UDP-27015 caveat above if you run tests on shared runners.