From b77983290b283ad7a760a3981c5eb9da3ba05629 Mon Sep 17 00:00:00 2001
From: "Michael B. Gale" <mbg@github.com>
Date: Thu, 30 Apr 2026 13:28:42 +0100
Subject: [PATCH] Fix `permutations` comment

---
 src/json/testing-util.ts | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/json/testing-util.ts b/src/json/testing-util.ts
index c534262b8..18c1bf06e 100644
--- a/src/json/testing-util.ts
+++ b/src/json/testing-util.ts
@@ -61,8 +61,17 @@ export function withSchemaMatrix<S extends json.Schema>(
     `value-for-${String(key)}`,
   ];
 
-  // Constructs an array of test objects, starting with `required` and adding
-  // acceptable values for any
+  // Constructs an array of test objects, starting with `required` and combining it with all
+  // possible states of each optional property. For example, with default settings:
+  //
+  // For { requiredKey: string }, we get: `[{ requiredKey: "some-string-value" }]`
+  //
+  // For { requiredKey: string, optionalKey?: string }, we get:
+  // [ { requiredKey: "some-string-value" },
+  //   { requiredKey: "some-string-value", optionalKey: undefined },
+  //   { requiredKey: "some-string-value", optionalKey: null },
+  //   { requiredKey: "some-string-value", optionalKey: "some-value" },
+  // ]
   const permutations = (keys: Array<keyof S>) => {
     if (keys.length === 0) return [required];