test(builtins): add Node + wasmtime + CI coverage for call AST

CI gap: zig build test-unit was not run by CI, so Zig-side unit
tests in src/builtins.zig and the new tests in src/eval.zig (call
startswith / count / unknown denies) were never validated upstream.

Fixes:
- ci.yml gains a test-unit job that runs zig build test-unit on
  ubuntu-latest. Independent of the build matrix; needs only the
  Zig toolchain.
- test/run.mjs gains 7 cases covering startswith / endswith /
  contains / count (with > comparator) and the unknown-builtin
  deny path.
- test/run_wasmtime.py gets the same 6 cases (parity with run.mjs).

Author: kanywst

test/run.mjs

@@ -354,6 +354,75 @@ check(
   0,
 );
 
+// ---------------------------------------------------------------------------
+// 8. call: builtin functions (startswith / endswith / contains / count)
+// ---------------------------------------------------------------------------
+const callStartswith = (path, prefix) => ({
+  type: 'call', name: 'startswith',
+  args: [
+    { type: 'ref', path: ['input', 'path'] },
+    { type: 'value', value: prefix },
+  ],
+});
+check('call startswith on input.path -> allow', decide({ path: '/admin/users' }, callStartswith('path', '/admin/')), 1);
+check('call startswith on input.path -> deny',  decide({ path: '/users' },        callStartswith('path', '/admin/')), 0);
+
+check(
+  'call endswith on host -> allow',
+  decide({ host: 'api.internal' }, {
+    type: 'call', name: 'endswith',
+    args: [
+      { type: 'ref', path: ['input', 'host'] },
+      { type: 'value', value: '.internal' },
+    ],
+  }),
+  1,
+);
+
+check(
+  'call contains in user-agent -> allow',
+  decide({ ua: 'Mozilla/5.0 Bot' }, {
+    type: 'call', name: 'contains',
+    args: [
+      { type: 'ref', path: ['input', 'ua'] },
+      { type: 'value', value: 'Bot' },
+    ],
+  }),
+  1,
+);
+
+// count compared to a literal, used in body position.
+check(
+  'call count > 2 over array -> allow',
+  decide({ perms: ['r', 'w', 'x'] }, {
+    type: 'gt',
+    left: { type: 'call', name: 'count', args: [{ type: 'ref', path: ['input', 'perms'] }] },
+    right: { type: 'value', value: 2 },
+  }),
+  1,
+);
+check(
+  'call count > 2 over array -> deny',
+  decide({ perms: ['r'] }, {
+    type: 'gt',
+    left: { type: 'call', name: 'count', args: [{ type: 'ref', path: ['input', 'perms'] }] },
+    right: { type: 'value', value: 2 },
+  }),
+  0,
+);
+
+// unknown builtin: lookup miss resolves to .nil, treated as falsy in
+// body position -> the synthetic `allow` rule fails -> deny (0). The
+// proxy-wasm shim treats any non-1 the same way (deny).
+check(
+  'call unknown builtin -> deny',
+  decide({}, {
+    type: 'call', name: 'made_up_function',
+    args: [{ type: 'value', value: 1 }],
+  }),
+  0,
+);
+
 if (failed > 0) {
   console.error(`\n${failed} test(s) failed`);
   exit(1);

test/run_wasmtime.py

@@ -238,6 +238,68 @@ def check(name: str, got, expected):
     0,
 )
 
+# ---------------------------------------------------------------------------
+# 8. call: builtin functions (startswith / endswith / contains / count)
+# ---------------------------------------------------------------------------
+check(
+    "call startswith on input.path -> allow",
+    decide({"path": "/admin/users"}, {
+        "type": "call", "name": "startswith",
+        "args": [
+            {"type": "ref", "path": ["input", "path"]},
+            {"type": "value", "value": "/admin/"},
+        ],
+    }),
+    1,
+)
+check(
+    "call startswith on input.path -> deny",
+    decide({"path": "/users"}, {
+        "type": "call", "name": "startswith",
+        "args": [
+            {"type": "ref", "path": ["input", "path"]},
+            {"type": "value", "value": "/admin/"},
+        ],
+    }),
+    0,
+)
+check(
+    "call endswith on host -> allow",
+    decide({"host": "api.internal"}, {
+        "type": "call", "name": "endswith",
+        "args": [
+            {"type": "ref", "path": ["input", "host"]},
+            {"type": "value", "value": ".internal"},
+        ],
+    }),
+    1,
+)
+check(
+    "call contains in user-agent -> allow",
+    decide({"ua": "Mozilla/5.0 Bot"}, {
+        "type": "call", "name": "contains",
+        "args": [
+            {"type": "ref", "path": ["input", "ua"]},
+            {"type": "value", "value": "Bot"},
+        ],
+    }),
+    1,
+)
+check(
+    "call count > 2 over array -> allow",
+    decide({"perms": ["r", "w", "x"]}, {
+        "type": "gt",
+        "left": {"type": "call", "name": "count", "args": [{"type": "ref", "path": ["input", "perms"]}]},
+        "right": {"type": "value", "value": 2},
+    }),
+    1,
+)
+check(
+    "call unknown builtin -> deny",
+    decide({}, {"type": "call", "name": "made_up_function", "args": [{"type": "value", "value": 1}]}),
+    0,
+)
+
 if failed:
     print(f"\n{failed} test(s) failed", file=sys.stderr)
     sys.exit(1)