Add initial test for Lua encoder

Boilerplate mostly copied from toml_test.go

pkg/yqlib/lua_test.go

@@ -0,0 +1,51 @@
+package yqlib
+
+import (
+	"bufio"
+	"fmt"
+	"testing"
+
+	"github.com/mikefarah/yq/v4/test"
+)
+
+var luaScenarios = []formatScenario{
+	{
+		skipDoc:      true,
+		description:  "Basic example",
+		input:        "hello: world\n? look: non-string keys\n: True\nnumbers: [123,456]\n",
+		expected:     "return {[\"hello\"]=\"world\";[{[\"look\"]=\"non-string keys\";}]=true;[\"numbers\"]={123,456,};};\n",
+		scenarioType: "encode",
+	},
+}
+
+func testLuaScenario(t *testing.T, s formatScenario) {
+	switch s.scenarioType {
+	case "encode":
+		test.AssertResultWithContext(t, s.expected, mustProcessFormatScenario(s, NewYamlDecoder(ConfiguredYamlPreferences), NewLuaEncoder(ConfiguredLuaPreferences)), s.description)
+	default:
+		panic(fmt.Sprintf("unhandled scenario type %q", s.scenarioType))
+	}
+}
+
+func documentLuaScenario(t *testing.T, w *bufio.Writer, i interface{}) {
+	s := i.(formatScenario)
+
+	if s.skipDoc {
+		return
+	}
+	switch s.scenarioType {
+	default:
+		panic(fmt.Sprintf("unhandled scenario type %q", s.scenarioType))
+	}
+}
+
+func TestLuaScenarios(t *testing.T) {
+	for _, tt := range luaScenarios {
+		testLuaScenario(t, tt)
+	}
+	genericScenarios := make([]interface{}, len(luaScenarios))
+	for i, s := range luaScenarios {
+		genericScenarios[i] = s
+	}
+	documentScenarios(t, "usage", "lua", genericScenarios, documentLuaScenario)
+}