return fake;

}

async function expectRejectCode(promise: Promise<unknown>, code: string): Promise<void> {

try {

await promise;

} catch (error) {

expect((error as NodeJS.ErrnoException).code).toBe(code);

return;

}

throw new Error(`expected rejection with code ${code}`);

}

describe("probePortFree", () => {

it("resolves false (not rejects) when bind returns EADDRINUSE", async () => {

mockCreateServer.mockReturnValue(makeErrServer("EADDRINUSE"));

it("rejects immediately for EADDRNOTAVAIL (non-retryable: host address not on any interface)", async () => {

mockCreateServer.mockReturnValue(makeErrServer("EADDRNOTAVAIL"));

await expect(probePortFree(9999, "192.0.2.1")).rejects.toMatchObject({ code: "EADDRNOTAVAIL" });

await expectRejectCode(probePortFree(9999, "192.0.2.1"), "EADDRNOTAVAIL");

});

it("rejects immediately for EACCES (non-retryable bind error)", async () => {

mockCreateServer.mockReturnValue(makeErrServer("EACCES"));

await expect(probePortFree(80, "0.0.0.0")).rejects.toMatchObject({ code: "EACCES" });

await expectRejectCode(probePortFree(80, "0.0.0.0"), "EACCES");

});

it("rejects immediately for other non-retryable errors", async () => {

mockCreateServer.mockReturnValue(makeErrServer("EINVAL"));

await expect(probePortFree(9999, "0.0.0.0")).rejects.toMatchObject({ code: "EINVAL" });

await expectRejectCode(probePortFree(9999, "0.0.0.0"), "EINVAL");

});

it("resolves true when the port is free", async () => {

// mockCreateServer would be called many times. We assert it's called exactly once.

mockCreateServer.mockClear();

mockCreateServer.mockReturnValue(makeErrServer("EACCES"));

await expect(

waitForPortBindable(80, { timeoutMs: 5000, intervalMs: 50 }),

).rejects.toMatchObject({ code: "EACCES" });

await expectRejectCode(waitForPortBindable(80, { timeoutMs: 5000, intervalMs: 50 }), "EACCES");

// Only one probe should have been attempted — no spinning through the retry loop.

expect(mockCreateServer).toHaveBeenCalledTimes(1);

});