1 files changed, 39 insertions, 0 deletions
diff --git a/test/cdp/evaluate-test.ts b/test/cdp/evaluate-test.ts
new file mode 100644
index 0000000..237ab40
--- /dev/null
+++ b/test/cdp/evaluate-test.ts
@@ -0,0 +1,39 @@
+import { test, describe } from "node:test";
+import assert from "node:assert/strict";
+import { evaluateJson } from "../../src/cdp/evaluate";
+import type { CdpSession } from "../../src/cdp/session";
+import { ok } from "../../src/util/result";
+
+const isNumberArray = (v: unknown): v is ReadonlyArray<number> =>
+  Array.isArray(v) && v.every((x) => typeof x === "number");
+
+const fakeSession = (payload: unknown): CdpSession =>
+  ({
+    call: async () => ok(payload),
+  }) as unknown as CdpSession;
+
+describe("evaluateJson", () => {
+  test("unwraps result.value and applies the guard", async () => {
+    const s = fakeSession({ result: { type: "object", value: [1, 2, 3] } });
+    const r = await evaluateJson(s, "[1,2,3]", isNumberArray);
+    assert.equal(r.success, true);
+    if (r.success) assert.deepEqual(r.data, [1, 2, 3]);
+  });
+
+  test("surfaces a page exception as an error", async () => {
+    const s = fakeSession({
+      result: { type: "undefined" },
+      exceptionDetails: { text: "ReferenceError: x is not defined" },
+    });
+    const r = await evaluateJson(s, "x", isNumberArray);
+    assert.equal(r.success, false);
+    if (!r.success) assert.match(r.error.message, /ReferenceError/);
+  });
+
+  test("rejects a value that fails the guard", async () => {
+    const s = fakeSession({ result: { type: "string", value: "nope" } });
+    const r = await evaluateJson(s, "'nope'", isNumberArray);
+    assert.equal(r.success, false);
+    if (!r.success) assert.equal(r.error.kind, "invalid_response");
+  });
+});