✅ How to write unit test for this?

[HttpGet("stream")]
public async Task StreamAsync(CancellationToken cancellationToken)
{
    Response.Headers.Append("Content-Type", "text/event-stream");

    while(!cancellationToken.IsCancellationRequested)
    {
        var sseEvent = new SseEvent<object>
        {
            Action = SseAction.Heartbeat,
            Timestamp = timeProvider.GetUtcNow().DateTime
        };

        var serializedSseEvent = Serialization.Serialize(sseEvent);

        await Response.WriteAsync($"{serializedSseEvent}", cancellationToken).ConfigureAwait(false);
        await Response.Body.FlushAsync(cancellationToken).ConfigureAwait(false);

        await Task.Delay(sseSettings.Timeout, cancellationToken).ConfigureAwait(false);
    }
}

[Test]
public async Task StreamAsync_ShouldWriteHeartbeatEvents()
{
    var cts = new CancellationTokenSource(TimeSpan.FromSeconds(3));

    await controller.StreamAsync(cts.Token).ConfigureAwait(false);
}