test(repro): match MCP-envelope escaping in trace_path repros (#480/#514/#546)

trace_path returns the MCP tool-result envelope
{"content":[{"type":"text","text":"<inner json>"}]}, so the inner json is
embedded as an escaped string value: the "callers"/"callees" keys appear as
backslash-escaped \"callers\" / \"callees\". These reproduce-first tests
hand-rolled strstr(resp, "\"callers\"") (unescaped), which can never match a
correctly escaped envelope, so they stayed RED even though the production
traversal is correct (verified by inspecting the inner json: callers/callees
populated, data_flow arg expressions surfaced, both import styles unioned).

Correct the assertions to the escaped form (the project's passing trace_path
tests in test_incremental.c use the same via resp_has_key) and assert
populated entries by qualified-name tail, keeping the empty-array guards so
the tests still RED on a genuinely-empty traversal. Production code unchanged.

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

tests/repro/repro_issue480.c

@@ -141,26 +141,26 @@ TEST(repro_issue480_trace_path_nonempty_with_calls) {
      * start-node lookup as the breakage site. */
     ASSERT_NULL(strstr(resp, "function not found"));
 
-    /* The "callers" key must appear — it is always emitted when direction
-     * includes "inbound" (even as an empty array), confirming we reached
-     * the BFS step. */
-    ASSERT_NOT_NULL(strstr(resp, "\"callers\""));
+    /* The response is the MCP tool-result envelope
+     *   {"content":[{"type":"text","text":"<inner trace_path json>"}]}
+     * so the inner json is embedded as a STRING value and its quotes are
+     * backslash-escaped: the "callers" key appears as \"callers\" in the
+     * serialized response. Match the escaped form — the project's own
+     * passing trace_path tests (test_incremental.c, via resp_has_key) do the
+     * same. (The earlier unescaped strstr could never match a correctly
+     * escaped MCP envelope, which is why this repro was mis-targeted.)
+     *
+     * The "callers" key must appear (always emitted for inbound). */
+    ASSERT_NOT_NULL(strstr(resp, "\\\"callers\\\""));
 
-    /* The "callers" array must be NON-EMPTY: the string "caller" must
-     * appear inside the response as the name of the calling function.
-     *
-     * WHY RED on buggy code:
-     *   cbm_store_bfs() starts from nodes[sel].id but that id does not
-     *   resolve to any edge endpoint in the graph, so visited_count == 0.
-     *   bfs_to_json_array() serialises an empty JSON array [].
-     *   strstr(resp, "\"caller\"") returns NULL → ASSERT_NOT_NULL fails.
-     *
-     * The two-part check below distinguishes the two bug symptoms:
-     *   1. empty array  → "callers\":[]"  present, no "\"caller\"" entry
-     *   2. name missing → "callers" array populated with wrong names
-     * Either way the final assertion is the one that must turn RED. */
-    ASSERT_NULL(strstr(resp, "\"callers\":[]")); /* empty array = traversal bug */
-    ASSERT_NOT_NULL(strstr(resp, "\"caller\"")); /* caller name in results    */
+    /* The "callers" array must be NON-EMPTY. WHY RED on the #480 bug:
+     * cbm_store_bfs() returning 0 hops serialises \"callers\":[] (no caller
+     * QN in the response), so BOTH the empty-array guard and the caller-QN
+     * assertion fire RED. We assert the caller's qualified-name tail
+     * "main.caller" (unambiguous vs the callee "main.callee", and immune to
+     * escaping) so a populated, correctly-named caller hop is required. */
+    ASSERT_NULL(strstr(resp, "\\\"callers\\\":[]")); /* empty array = traversal bug */
+    ASSERT_NOT_NULL(strstr(resp, "main.caller"));    /* caller QN in results       */
 
     free(resp);
     rh_cleanup(&lp, store);

tests/repro/repro_issue514.c

@@ -164,13 +164,17 @@ TEST(repro_issue514_data_flow_surfaces_arg_expr) {
     /* The response must not be an error -- the node must be found. */
     ASSERT_NULL(strstr(resp, "function not found"));
 
-    /* The "callees" key must appear (direction=outbound always emits it). */
-    ASSERT_NOT_NULL(strstr(resp, "\"callees\""));
+    /* The response is the MCP tool-result envelope (inner json embedded as an
+     * escaped string value), so the "callees" key appears as \"callees\".
+     * Match the escaped form (see repro_issue480 / test_incremental's
+     * resp_has_key idiom). */
+    ASSERT_NOT_NULL(strstr(resp, "\\\"callees\\\""));
 
-    /* The callees array must be non-empty: "callee" must appear as a hop.
-     * If this fires RED, the CALLS traversal is broken (separate from #514). */
-    ASSERT_NULL(strstr(resp, "\"callees\":[]"));
-    ASSERT_NOT_NULL(strstr(resp, "\"callee\""));
+    /* The callees array must be non-empty: the callee's QN tail "service.callee"
+     * must appear as a hop (unambiguous + escaping-proof). RED if the CALLS
+     * traversal is broken (separate from #514). */
+    ASSERT_NULL(strstr(resp, "\\\"callees\\\":[]"));
+    ASSERT_NOT_NULL(strstr(resp, "service.callee"));
 
     /*
      * THE CORE ASSERTION FOR BUG #514:

tests/repro/repro_issue546.c

@@ -219,8 +219,10 @@ TEST(repro_issue546_dts_split_caller_set) {
      * itself has a problem unrelated to #546. */
     ASSERT_NULL(strstr(resp, "function not found"));
 
-    /* "callers" key must appear (always emitted when direction is inbound). */
-    ASSERT_NOT_NULL(strstr(resp, "\"callers\""));
+    /* "callers" key must appear (always emitted when direction is inbound).
+     * The response is the MCP envelope (inner json embedded as an escaped
+     * string), so the key appears as \"callers\" — match the escaped form. */
+    ASSERT_NOT_NULL(strstr(resp, "\\\"callers\\\""));
 
     /* The callers array must not be empty — at least the internalConsumer
      * (whose relative-path import is reliably resolved) must appear.
@@ -230,7 +232,7 @@ TEST(repro_issue546_dts_split_caller_set) {
      *   externalConsumer is there; internalConsumer's edge is on the impl
      *   node, so this check fires RED immediately (callers:[]) or wrong name.
      */
-    ASSERT_NULL(strstr(resp, "\"callers\":[]")); /* empty = traversal totally wrong */
+    ASSERT_NULL(strstr(resp, "\\\"callers\\\":[]")); /* empty = traversal totally wrong */
 
     /* ── PRIMARY ASSERTION: BOTH callers must appear in the response ─────
      *