chore: create Lua test helper (#532)

* Create lua test helper

Signed-off-by: James Hillyerd <james@hillyerd.com>

* Assert labels

Signed-off-by: James Hillyerd <james@hillyerd.com>

---------

Signed-off-by: James Hillyerd <james@hillyerd.com>

pkg/test/lua.go

@@ -0,0 +1,90 @@
+package test
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/cosmotek/loguago"
+	"github.com/rs/zerolog"
+	lua "github.com/yuin/gopher-lua"
+)
+
+// LuaInit holds useful test globals.
+const LuaInit = `
+	local logger = require("logger")
+
+	async = false
+	asserts_ok = true
+
+	-- With async: marks tests as failed via asserts_ok, logs error.
+	-- Without async: erroring when tests fail.
+	function assert_async(value, message, label)
+		if not value then
+			if label then
+				message = string.format("%s for %s", message, label)
+			end
+
+			if async then
+				logger.error(message, {from = "assert_async"})
+				asserts_ok = false
+			else
+				error(message)
+			end
+		end
+	end
+
+	-- Verifies plain values and list-style tables.
+	function assert_eq(got, want, label)
+		if type(got) == "table" and type(want) == "table" then
+			assert_async(#got == #want,
+				string.format("got %d elements, wanted %d", #got, #want), label)
+
+			for i, gotv in ipairs(got) do
+				local wantv = want[i]
+				assert_eq(gotv, wantv,
+					string.format("got[%d] = %q, wanted %q", gotv, wantv), label)
+			end
+
+			return
+		end
+
+		assert_async(got == want, string.format("got %q, wanted %q", got, want), label)
+	end
+
+	-- Verifies string want contains string got.
+	function assert_contains(got, want, label)
+		assert_async(string.find(got, want),
+			string.format("got %q, wanted it to contain %q", got, want), label)
+	end
+`
+
+// NewLuaState creates a new Lua LState initialized with logging and the test helpers in `LuaInit`.
+//
+// Returns a pointer to the created LState and a string builder to hold the log output.
+func NewLuaState() (*lua.LState, *strings.Builder) {
+	output := &strings.Builder{}
+	logger := loguago.NewLogger(zerolog.New(output))
+
+	ls := lua.NewState()
+	ls.PreloadModule("logger", logger.Loader)
+	if err := ls.DoString(LuaInit); err != nil {
+		panic(err)
+	}
+
+	return ls, output
+}
+
+// AssertNotified requires a truthy LValue on the notify channel.
+func AssertNotified(t *testing.T, notify chan lua.LValue) {
+	t.Helper()
+	select {
+	case reslv := <-notify:
+		// Lua function received event.
+		if lua.LVIsFalse(reslv) {
+			t.Error("Lua responsed with false, wanted true")
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("Lua did not respond to event within timeout")
+	}
+}