test: add coverage for find_usages, find_dependencies, and serializer roundtrip (6 new tests)

[github-actions]

What gap was identified

Two distinct areas had zero test coverage:

1. find_usages and find_dependencies — src/graph/queries.rs exports these two general graph-traversal methods on RefGraph, but they had no tests. The existing query tests only covered the type-filtered variants (find_incoming_transitions, find_outgoing_transitions, find_action_invokers, etc.), leaving the foundational find_usages / find_dependencies methods completely unexercised.

2. Serializer roundtrip for start_agent and system blocks — tests/test_serializer_roundtrip.rs covered config, topic, variables, connection, language, and before/after-reasoning, but had no roundtrip test for the start_agent block (name, description, reasoning, reasoning actions) or for the system: block's messages: sub-block (welcome / error strings).

Files modified

File	Change
src/graph/queries.rs	+3 unit tests
tests/test_serializer_roundtrip.rs	+3 roundtrip tests

New tests

src/graph/queries.rs

• test_find_usages_of_transition_target_topic — topic_a has a TransitionsTo edge to topic_b; find_usages(topic_b_idx) must return topic_a as a source because find_usages returns all incoming-edge sources regardless of edge type.

• test_find_usages_of_topic_routed_from_start_agent — start_agent has a Routes edge to topic_a; find_usages(topic_a_idx) must include the start_agent node as a source.

• test_find_dependencies_of_start_agent_returns_routed_topic — start_agent routes to topic_a via a Routes edge; find_dependencies(start_agent_idx) must include topic_a because find_dependencies returns all outgoing-edge targets.

tests/test_serializer_roundtrip.rs

• test_roundtrip_start_agent_basic — a start_agent block with a name, description, and reasoning instructions serializes and re-parses with the name and reasoning preserved.

• test_roundtrip_start_agent_with_reasoning_actions — two reasoning actions inside start_agent survive a full roundtrip without being dropped or duplicated.

• test_roundtrip_system_block_with_messages — the system: block's messages: sub-block (welcome + error strings) survives parse → serialize → parse with the welcome message content intact.

Generated by Test Coverage Improver

Generated by Test Coverage Improver