From cbc177d5d917c4f5344abbc144b37f0e12fcbf70 Mon Sep 17 00:00:00 2001
From: Evin Sellin <evinism@gmail.com>
Date: Sat, 20 Jan 2024 11:03:30 -0800
Subject: [PATCH] reproduce error

---
 src/lib/lambda/__tests__/bReduction.spec.js | 39 ++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/src/lib/lambda/__tests__/bReduction.spec.js b/src/lib/lambda/__tests__/bReduction.spec.js
index c055b3f..836b0fd 100644
--- a/src/lib/lambda/__tests__/bReduction.spec.js
+++ b/src/lib/lambda/__tests__/bReduction.spec.js
@@ -1,7 +1,6 @@
 import { assert } from "chai";
 import { bReduce } from "../operations";
 import { purgeAstCache } from "../util";
-import { parseTerm } from "../parser";
 
 describe("Beta Reductions", function () {
   it("Beta reduces a redex", function () {
@@ -241,4 +240,42 @@ describe("Beta Reductions", function () {
     };
     assert.deepEqual(purgeAstCache(bReduce(ast)), expected);
   });
+
+  it("can't replace a variable with itself.", () => {
+    const ast = {
+      type: "application",
+      left: {
+        type: "function",
+        argument: "ε₁",
+        body: {
+          type: "application",
+          left: {
+            type: "function",
+            argument: "a",
+            body: {
+              type: "function",
+              argument: "b",
+              body: { type: "variable", name: "b" },
+            },
+          },
+          right: { type: "variable", name: "ε₁" },
+        },
+      },
+      right: { type: "variable", name: "b" },
+    };
+    const expected = {
+      type: "application",
+      left: {
+        type: "function",
+        argument: "a",
+        body: {
+          type: "function",
+          argument: "b",
+          body: { type: "variable", name: "b" },
+        },
+      },
+      right: { type: "variable", name: "b" },
+    };
+    assert.deepEqual(purgeAstCache(bReduce(ast)), expected);
+  });
 });