Testing

Mux test blocks are named, top-level blocks:

Mux

The built-in assert always takes a boolean condition and a message. It panics immediately when the condition is false, making failed invariants visible in the test output. Use ordinary comparisons and optional/result inspection methods such as is_some() or is_ok() to form the condition; there is no assertion package to import.

The body uses ordinary Mux statements and standard-library helpers. Test blocks are omitted from normal application builds; they are collected and run by the mux test command. Keep setup in regular functions so it can be shared by multiple named tests.

Run tests from a project containing tests/**/*.mux, or pass source files explicitly:

mux test
mux test tests/math.mux --filter addition --jobs 1
mux test --format json > test-results.json
mux test --tag integration
mux test --coverage

The runner starts each named test in its own process, runs tests concurrently by default, and applies a 60-second timeout (override it with --timeout). Human, JSON, and JUnit output formats are available.

Pass --coverage to instrument the generated test programs and write a merged lcov.info report. The report includes statement and branch records for the original Mux files, including imported functions. Coverage is opt-in, so normal builds and test runs stay uninstrumented.

Instrumented sites are recorded separately from runtime hits, so unvisited statements and branch outcomes remain visible in LCOV with zero coverage. Runtime hit counts are aggregated by source site, so looping does not grow the coverage file. Each test process writes its counts at normal exit. A missing completion marker, such as after a crash or failed write, makes coverage collection fail rather than publish an incomplete report.

An optional annotation immediately above a test can override its timeout and attach filtering/reporting tags:

Mux

Annotation values use key=value syntax. timeout is in seconds and must be positive; tags contain letters, numbers, _, or -. --tag selects tests carrying an exact tag.

Test names are quoted and must be non-empty. A test block cannot be nested in a function, class, or another block.