Add simple test for TRANSITION_FNS

* src/paca.mjs (TRANSITION_FNS): Add trailing underscore to ignored
  arguments, even though it breaks the name of the `_state` and
  `context` destructuring arguments.
* tests/paca.mjs (test_TRANSITION_FNS): Add new test function with a
  single case for each transition character.  Since these transitions
  are unconditional and contain no logic, this single sample test is
  enough to cover for all of its behaviour.

2 files changed, 35 insertions, 2 deletions

diff --git a/src/paca.mjs b/src/paca.mjs
index e8ec542..c1bead1 100644
--- a/src/paca.mjs
+++ b/src/paca.mjs
@@ -107,12 +107,12 @@ const STATE_FNS = {
 };
 
 const TRANSITION_FNS = {
-	"\\": ({ out, state, context }, char, index, next) => ({
+	"\\": ({ out, _state, context }, _char, _index, _next) => ({
 		out,
 		state: ConcatStep.ESCAPING,
 		context,
 	}),
-	"{": ({ out, state, context }, char, index, next) => ({
+	"{": ({ out, _state, _context }, _char, _index, _next) => ({
 		out,
 		state: ConcatStep.RANGE,
 		context: {
diff --git a/tests/paca.mjs b/tests/paca.mjs
index 0ba2d61..b259968 100644
--- a/tests/paca.mjs
+++ b/tests/paca.mjs
@@ -3,6 +3,7 @@ import { explode, reduced, reductions, runTests } from "sjs";
 import {
 	SyntaxError,
 	ConcatStep,
+	TRANSITION_FNS,
 	shouldConcat,
 	isOperator,
 	numFromDigits,
@@ -43,6 +44,37 @@ import {
 
 
 
+const test_TRANSITION_FNS = t => {
+	t.start("TRANSITION_FNS");
+
+	t.testing("\"\\\\\" depends on `out` and `context`", () => {
+		t.assertEq(
+			TRANSITION_FNS["\\"](
+				{ out: 1, context: 2 },
+				null,
+				null,
+				null,
+			),
+			{ out: 1, context: 2, state: "escaping" },
+		);
+	});
+
+	t.testing("\"{\" only depends on `out`", () => {
+		t.assertEq(
+			TRANSITION_FNS["{"]({ out: "" }, null, null, null),
+			{
+				out:     "",
+				state:   "range",
+				context: {
+					from:  [],
+					to:    [],
+					where: "from",
+				},
+			},
+		);
+	});
+};
+
 const test_shouldConcat = t => {
 	t.start("shouldConcat()");
 
@@ -2351,6 +2383,7 @@ const test_compile = t => {
 
 
 runTests([
+	test_TRANSITION_FNS,
 	test_shouldConcat,
 	test_isOperator,
 	test_numFromDigits,