Write unit tests for SSA optimization passes in the Noir compiler's noirc_evaluator.
npx skills add https://github.com/noir-lang/noir --skill noir-ssa-tests
Please help me install this Agent Skill. Skill: noir-ssa-tests Source: https://github.com/noir-lang/noir/tree/main/.claude/skills/noir-ssa-tests Command: npx skills add https://github.com/noir-lang/noir --skill noir-ssa-tests
Writing tests for SSA optimization passes in the Noir compiler often stops at snapshot assertions, which pin output shape but cannot catch miscompilations where the pass silently changes what the program computes. This Skill guides you to write tests that prove a pass preserves execution semantics, not just structure.
assert_pass_does_not_affect_execution to interpret SSA before and after a pass and assert identical results, including failure behavior like which constraint fails.assert_ssa_snapshot!, or assert a pass leaves input untouched with assert_ssa_does_not_change.nargo compile --show-ssa-pass, build interpreter inputs with Value constructors, and handle path-sensitive bugs with one run per input.ConstrainEqFailed error is preserved, and snapshots the transformed SSA.Ask the AI to write a regression test for an SSA pass in compiler/noirc_evaluator/src/ssa/opt/ that proves the pass preserves execution semantics and snapshots its output.
High-intent search queries and answers about installing and using this skill.
Add a test in the inline mod tests at the bottom of the pass's file under compiler/noirc_evaluator/src/ssa/opt/. Parse textual SSA with Ssa::from_str, run the pass through assert_pass_does_not_affect_execution, then snapshot the result with assert_ssa_snapshot!.
A snapshot only pins the shape of the output SSA, so a miscompiling pass produces a stable, plausible snapshot that gets accepted. Pair snapshots with assert_pass_does_not_affect_execution, which interprets the SSA before and after the pass and asserts the results match.
Use assert_ssa_does_not_change(src, pass) for a one-line no-op test asserting the pass leaves the input completely alone. For comparing against an explicit expected string, use assert_normalized_ssa_equals instead.
Compile a real Noir program with cargo run -q -p nargo_cli -- compile --silence-warnings --force --show-ssa-pass <label> to capture actual SSA. The grammar is defined in compiler/noirc_evaluator/src/ssa/parser/, so grep existing tests when unsure about syntax.
Fall back to a snapshot-only test when the pass intentionally changes semantics, main calls a foreign function, the program exceeds the interpreter's step budget, or the pass only touches metadata the interpreter never observes. Document the reason in a comment.
A shallow clone shares an array's backing storage, so an in-place array_set in the first interpretation corrupts the second run's inputs. Use assert_pass_does_not_affect_execution, which deep-copies inputs via Value::snapshot_args for each run.
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