Lua steps for godog

This module implements godog step definitions that run arbitrary Lua scripts (inline or from file), with access to variables shared through github.com/godogx/vars.

It is useful for scenarios that need a bit of scripted logic (computing a value, transforming a variable, building test data) that would be awkward to express with plain gherkin steps.

Setup

vs := &vars.Steps{}
ls := &luasteps.Steps{VS: vs} // share vars store with vars.Steps

ScenarioInitializer: func(s *godog.ScenarioContext) {
    vs.Register(s)
    ls.Register(s)
}

Lua API

Scripts run with the full Lua standard library available, plus a vars module bound to the shared variable store. Variable names include the vars prefix (default $), same as in github.com/godogx/vars steps and tables.

vars.set("$foo", "bar")            -- create or update a variable
local v, found = vars.get("$foo")  -- read a variable
local exists = vars.has("$foo")
vars.delete("$foo")                -- remove a variable
local all = vars.all()             -- table of all variables

Values are converted between Go and Lua: strings, booleans, numbers, nil, and JSON-like tables (arrays and objects) round-trip transparently.

Lua's built-in assert(condition, message) is the natural way to make a script fail: any Lua runtime error, including a failed assert, fails the godog step with that error message.

assert(vars.has("$order"), "$order must be set before this step")

Attachments

godog.attach(name, body, mediaType) attaches a piece of test context to the step's result, the same mechanism godogx/httpsteps uses to expose HTTP request/response details. It shows up in report formats that render attachments (e.g. cucumber JSON, pretty).

godog.attach("note", "plain text body")               -- MediaType defaults to "text/plain"
godog.attach("note", "plain text body", "text/html")  -- explicit MediaType
godog.attach("order", {id = 42, total = 29.97})       -- a table is JSON-encoded,
                                                       -- MediaType defaults to "application/json"

Attachments made before a script fails (e.g. a failed assert) are still recorded, so they remain useful for debugging the failure.

Advanced Lua Configuration

Steps.NewState creates the *lua.LState used for each script run, the extension point for lower-level control: sandboxing, tuning limits, or registering extra Go functions/modules (by hand, or with a binding library like gopher-luar).

ls := &luasteps.Steps{
    VS: vs,
    NewState: func() *lua.LState {
        // Sandbox scripts: no os/io libraries available to Lua.
        L := lua.NewState(lua.Options{SkipOpenLibs: true})
        lua.OpenBase(L)
        lua.OpenString(L)
        lua.OpenTable(L)
        lua.OpenMath(L)

        return L
    },
}

If NewState is nil, lua.NewState() is used, which opens the full standard library. The vars module is always registered after NewState returns.

Step Definitions

Run an inline Lua script.

When I run lua script
  """
  vars.set("$foo", "bar")
  """

Run a Lua script from a file.

When I run lua script from file
  """
  testdata/script.lua
  """