test: cover logger metadata serialization

tests/logger.test.ts

@@ -0,0 +1,57 @@
+import { describe, expect, it } from "vitest";
+import { formatLogMetadataForTest, serializeLogValueForTest } from "../src/logger";
+
+class TestError extends Error {
+  public code = "TEST_CODE";
+  public statusCode = 418;
+
+  constructor() {
+    super("test failure");
+    this.name = "TestError";
+  }
+}
+
+describe("logger serialization", () => {
+  it("serializes Error values with stable fields", () => {
+    const serialized = serializeLogValueForTest(new TestError());
+
+    expect(serialized).toMatchObject({
+      name: "TestError",
+      message: "test failure",
+      code: "TEST_CODE",
+      statusCode: 418,
+    });
+    expect(serialized).toHaveProperty("stack");
+  });
+
+  it("serializes nested error metadata keys", () => {
+    const error = new TestError();
+
+    expect(formatLogMetadataForTest({ error, err: error, reason: error })).toMatchObject({
+      error: {
+        name: "TestError",
+        message: "test failure",
+        code: "TEST_CODE",
+        statusCode: 418,
+      },
+      err: {
+        name: "TestError",
+        message: "test failure",
+        code: "TEST_CODE",
+        statusCode: 418,
+      },
+      reason: {
+        name: "TestError",
+        message: "test failure",
+        code: "TEST_CODE",
+        statusCode: 418,
+      },
+    });
+  });
+
+  it("preserves plain metadata", () => {
+    expect(
+      formatLogMetadataForTest({ context: "bot", signal: "SIGINT", count: 2 }),
+    ).toEqual({ context: "bot", signal: "SIGINT", count: 2 });
+  });
+});