Why is testing a network harder than testing a single application?

A network's behaviour is collective: it emerges from the configurations of many individual devices. Traditionally each is managed by hand through different interfaces, which is slow, very error-prone and risky.

An application can often be tested in isolation. A network cannot, because whether traffic from A reaches B depends on every router, switch and firewall along the path agreeing on routes, VLANs and rules. A single wrong line on one device can break connectivity somewhere else entirely.

In traditional environments, connectivity and function are maintained manually, device by device, often through different interfaces (CLI on one vendor, a web GUI on another). Checking that the whole thing works means logging into many boxes and reading output by eye.

The stakes keep rising. Networks get more complex and carry more varied, performance-sensitive traffic (voice, video, storage), so a mistake now risks both security and performance at once. That is the case for automated network testing.