Add test to ensure no regression on side effect bug

tests/known-bugs/solution.txt

@@ -0,0 +1 @@
+foo = \ x j c . x c ()

tests/known-bugs/test.js

@@ -0,0 +1,18 @@
+import {readFileSync} from "fs";
+import {assert, config as chaiConfig} from "chai";
+chaiConfig.truncateThreshold = 0;
+
+import * as LC from "../../src/lambda-calculus.js";
+LC.configure({ purity: "Let", numEncoding: "None" });
+
+const solutionText = readFileSync(new URL("./solution.txt", import.meta.url), {encoding: "utf8"});
+const { foo } = LC.compile(solutionText);
+
+describe("No side effects", () => {
+  it("The initial failed call used to cause the second call to behave weirdly", () => {
+    try {
+      foo("hi")("there")("world")
+    } catch {}
+    assert.strictEqual( foo(null).term.toString(), "\\ j c . x c ()" );
+  });
+});