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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →NetChaos lets Go developers test how application code responds to simulated network faults from an ordinary go test run. It provides in-process implementations of net.Conn and net.Listener, so you can exercise retry, timeout, backoff, and circuit-breaker logic without running a proxy or daemon. It tests behavior against a simulated transport—not whether a deployed service survives real network conditions.
What NetChaos does in a Go test
NetChaos creates a simulated network and peers that communicate through simulated connections. Your test can then introduce faults and observe how the application reacts, while remaining inside the Go test process. The project describes this as a focused way to test resilience logic without setting up separate infrastructure. See the NetChaos package documentation.
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That makes NetChaos useful for questions such as: does a client retry after a connection reset, respect a timeout when latency rises, or stop issuing requests when a circuit breaker opens? The author framed the motivating question as, “does this actually work when the network starts failing?” — João Paulo Gomes Rodrigues, NetChaos author. His NetChaos article provides the project’s original motivation.
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Network faults you can simulate
The v0.3.0 documentation describes these fault types:
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- Latency: add delay to communication, including delay that can be used with virtual time.
- Packet loss: drop some traffic.
- Bandwidth throttling: constrain data transfer.
- Packet duplication: deliver duplicate data.
- Data corruption: alter data in transit.
- Network partitions: prevent communication across a partition.
- Mid-stream connection reset: interrupt an established connection.
The v0.3.0 notes also describe changing duplication and corruption rates while a test is running, bounded waits when dialing, argument validation for partition, heal, and reset operations, and trace events that report payload size and corruption location. The package documentation is the reference for the specific API and behavior available in that release.
Version, Go requirement, and virtual time
The package page lists NetChaos v0.3.0 and requires Go 1.25 or later, citing its integration with testing/synctest. The documented installation command for that release is:
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The project describes its API as stable, but not frozen before v1.0.0. Check the package page for the current release and Go requirement before adding it to a project; both can change.
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NetChaos can use testing/synctest to virtualize waiting associated with injected latency. Create the simulated network inside the synctest bubble that will use it. The package documentation cautions that channels and timers created inside a bubble cannot safely be used from outside it.
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How reproducible are seeded tests?
A seed can make a fault sequence reproducible when the test makes the same sequence of network method calls. That qualification matters: if multiple connections are established concurrently, scheduler order can affect their connection ordinals and therefore the sequence they receive. For more predictable replay, establish connections in a fixed order before starting concurrent I/O.
In other words, a seed helps repeat a controlled sequence; it does not guarantee identical outcomes for every concurrent execution regardless of scheduling.
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- Cable state testing (2-wire): Line DC detecting, anode and cathode determination,Ringing signal detecting open, short and cross circuit testing
- Cable Type: RJ11 Telephone cable and RJ45 LAN cable
- Connectors: Ethernet Cat 5, Ethernet Cat 5e, Ethernet Cat 6, Ethernet Cat 7, RJ11 6P and RJ45 8P
- Power Source: DC9V Battery Required (not included)
When to use NetChaos—and when not to
| Approach | Boundary and network | Best fit |
|---|---|---|
| NetChaos | In-process simulated transport | Test application decisions such as retries, timeouts, backoff, and circuit-breaker transitions with network faults. |
| Toxiproxy | External proxy; real sockets | Exercise a service across a process boundary when integration behavior over actual sockets matters. See Toxiproxy. |
| Production chaos engineering platforms | Running infrastructure and its real blast radius | Deliberately test the behavior of deployed systems. |
| Full-program deterministic simulation such as gosim | Broader program or environment simulation | Control behavior beyond the network layer, such as disk behavior, system calls, or scheduling. See gosim. |
These tools address different testing boundaries rather than forming a universal ranking. NetChaos is a narrow seam for network-related application logic. It does not prove that real sockets, operating-system networking, a deployed service, or production infrastructure will behave the same way under degraded conditions. Use a proxy when real-socket integration is the question, and production chaos testing when the question concerns a running system’s failure impact.
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A practical decision checklist
- Choose NetChaos if the test should stay in Go and focus on how application logic responds to injected network faults.
- Choose an external proxy if you need to test communication over real sockets or across separate processes.
- Choose a production chaos approach if you need evidence about deployed infrastructure and its blast radius.
- Choose broader deterministic simulation if controlling non-network behavior is essential.
- For seeded NetChaos tests, keep connection establishment order fixed when reproducibility matters.
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