mock-nexus

A mock Sonatype Nexus raw server with a failure-scenario table: the shared conformance fixture of this repository. The Rust test suites, the Python reference suite, a human debugging a client, and external harnesses all drive the same list of scenarios, so a behavior pinned against the mock is pinned against one contract, not against whoever ran the test.

Std-only: the runtime has one dependency (serde_json), one request per connection, Connection: close everywhere. No keep-alive, no chunked responses, no async runtime: every byte on the wire is either storage contract or a named failure mode, and nothing else competes for attention.

Quick starts

As a library in a Rust test:

use mock_nexus::{MockNexus, Scenario};

let server = MockNexus::start(Scenario::Atomic)?;
let url = format!("{}repository/raw-main/1.0.0/app.bin", server.base_url());
server.insert("repository/raw-main/1.0.0/app.bin", b"bytes")?;

As a binary in a terminal or a script:

cargo run -p mock-nexus -- atomic --port 8080
# listening http://127.0.0.1:8080

As a seeded instance with composed behavior:

cargo run -p mock-nexus -- atomic --seed-dir ./fixture --config rate-limit.json

The full surface: the mock server reference (scenario table, flags, --seed-dir, --config, the library API, and how to add a scenario), and the generated wire invariants page.

Presets and composition

Thirty-three named scenarios cover the failure modes a correct client must survive: transport cuts, framing lies, pacing, auth gates, service-API shapes, integrity litter. Each is one Scenario variant, one name in --print-scenarios, one row on the invariants page.

When a test needs a combination no preset expresses, compose a Spec instead:

use mock_nexus::{MockNexus, Spec};

let server = MockNexus::start_spec(
    Spec::atomic().with_auth("ci", "secret").with_flaky(1),
)?;

Presets stay canonical and guarded. Specs are code-level composition and never enter the contract tables.

The drift guards

The scenario table is a contract held in four places: the Rust enum, the binary's name table, the generated invariants page, and the Python suite's classification table. Four drift tests refuse a change that updates one place and not the others. Adding a scenario is a documented, mechanical procedure. Changing one means touching all four in the same commit.