test(selection-test): cheap-fill M3 gap + Coverage Statements (Test-Cov Phase 2.5)

3 mutations tested. 2 caught, 1 uncaught (M3: add unregistered-handle guard absent).
Cheap-fill: added pcall assertions for add(unregistered) and toggle(unregistered).

README.md

@@ -0,0 +1,48 @@
+# sporel-module-lib-core.selection-test
+
+P.3.6 reference test-module — validates `lib-core.selection` API contracts
+via the `engine.test.*` assertion surface.
+
+- Module-ID: `lib-core.selection-test`
+- Version: `0.1.0`
+- Kind: `test-module` (headless; runs init() once + exits)
+- Spec: `meta/docs/superpowers/specs/2026-05-14-p3-6-lib-selection-design.md`
+
+## Run
+
+```bash
+Sporel.exe --test-libs=lib-core.selection-test
+```
+
+Output is TAP version 13 on stdout; exit-code = failure-count (0 = all pass).
+
+## Coverage Statements (2026-05-16 Fault-Injection Audit)
+
+Verified via deliberate-mutation in fixture-mirror; mutations reverted after observation.
+
+### Caught Mutations
+
+| # | Mutation | Caught by |
+|---|---|---|
+| M1 | `M.contains` prefixed with `do return false end` (always false) | Assertions "add → contains" (ok 6) and "toggle adds when absent" (ok 9) — 2 failures |
+| M2 | `M.count` prefixed with `do return 0 end` (always zero) | Assertion "count = 1 after add" (ok 7) — expected 1 got 0 |
+
+### Uncaught Mutations (Gaps)
+
+| # | Mutation | Why uncaught | Severity |
+|---|---|---|---|
+| M3 | `M.add` unregistered-handle guard removed (any handle accepted silently) | No test calls `add(unregistered_handle)` and expects an error | Medium |
+
+**Resolution per Gap:**
+- Gap M3: Cheap-fill applied — two `pcall` error assertions added for `add(99999)` and `toggle(99999)` (commit see below).
+
+### Cheap-Gap-Fills Applied
+
+| Gap | New Assertion | Re-Inject Verifies |
+|---|---|---|
+| M3 | `add(unregistered) errors` — `pcall(function() selection.add(99999) end)` must return false | ✓ |
+| M3 | `toggle(unregistered) errors` — `pcall(function() selection.toggle(99999) end)` must return false | ✓ |
+
+### Tested Production-Lib Surface
+
+`lib-core.selection` v0.1.0 — Tests cover: `register`, `unregister`, `count_registered`, `is_empty`, `count`, `contains`, `add`, `remove`, `toggle`, `clear`, `drag_threshold`, `set_drag_threshold`, `drag_state`, `box_rect`, `enabled`, `set_enabled`, `set_drag_box_color`, `drag_box_color`, `set_highlight_color`, `highlight_color`.

init.lua

@@ -64,9 +64,13 @@ function M.run_tests(ctx)
     T.assert(hc[1]==50 and hc[2]==60 and hc[3]==70 and hc[4]==80,
              "set_highlight_color writes correctly")
 
-    -- Error-Handling (1)
+    -- Error-Handling (3)
     local ok = pcall(function() selection.set_drag_threshold(-1) end)
     T.assert(not ok, "set_drag_threshold(-1) errors")
+    local ok2 = pcall(function() selection.add(99999) end)
+    T.assert(not ok2, "add(unregistered) errors")
+    local ok3 = pcall(function() selection.toggle(99999) end)
+    T.assert(not ok3, "toggle(unregistered) errors")
 end
 
 return M