Testing your scripts¶

Replacing working Lua in a production path needs evidence. Two things supply most of it, and both are short.

Snapshot the Lua¶

.lua is the whole script, so a golden test is a string comparison — and the diff against the Lua you are replacing is the review.

from pathlib import Path

GOLDEN = Path(__file__).parent / "golden" / "rate_limit.lua"


def test_generated_lua_is_unchanged():
    assert rate_limit.lua == GOLDEN.read_text()

The header path is repo-relative, so this is stable across machines and CI. Use @script(header=False) if you would rather compare the body alone — see What it compiles to.

Run the behaviour, without a server¶

fakeredis embeds a real Lua interpreter, so your script executes for real against an in-process server:

import fakeredis


def test_rate_limit_refuses_past_the_limit():
    client = fakeredis.FakeRedis()

    assert rate_limit(client, key="u:42", limit=2, ttl=60) == 1
    assert rate_limit(client, key="u:42", limit=2, ttl=60) == 0
    assert rate_limit(client, key="u:42", limit=2, ttl=60) == -1

Install it with:

uv add --dev "fakeredis[lua]"

The lua extra is what brings the interpreter. This library's own suite runs that way and against a real Redis in CI, and the two agree — including on reply conversion, which is the part you would most want a real server for.