From e0e70d05f2024c857cefc1fe65e3c5f5e7e44727 Mon Sep 17 00:00:00 2001
From: harshiltewari2004 <harshiltewari2004@gmail.com>
Date: Sun, 10 May 2026 19:16:17 +0530
Subject: [PATCH 1/2] Rename States.getDiff to takeDiff to reflect mutation
 semantics

---
 src/core/States.js      | 2 +-
 src/core/p5.Renderer.js | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/core/States.js b/src/core/States.js
index a70a6300c2..bc5a8a9a41 100644
--- a/src/core/States.js
+++ b/src/core/States.js
@@ -14,7 +14,7 @@ export class States {
     this[key] = value;
   }
 
-  getDiff() {
+  takeDiff() {
     const diff = this.#modified;
     this.#modified = {};
     return diff;
diff --git a/src/core/p5.Renderer.js b/src/core/p5.Renderer.js
index 8467695bf8..ae5082644a 100644
--- a/src/core/p5.Renderer.js
+++ b/src/core/p5.Renderer.js
@@ -135,7 +135,7 @@ class Renderer {
   // and push it into the push pop stack
   push() {
     this._pushPopDepth++;
-    this._pushPopStack.push(this.states.getDiff());
+    this._pushPopStack.push(this.states.takeDiff());
   }
 
   // Pop the previous states out of the push pop stack and

From b54e54073301ad8fda4555275f7092aa2815de0f Mon Sep 17 00:00:00 2001
From: harshiltewari2004 <harshiltewari2004@gmail.com>
Date: Sun, 10 May 2026 19:17:25 +0530
Subject: [PATCH 2/2] Add unit tests for States class

---
 test/unit/core/States.js | 70 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 test/unit/core/States.js

diff --git a/test/unit/core/States.js b/test/unit/core/States.js
new file mode 100644
index 0000000000..d4b2b56a35
--- /dev/null
+++ b/test/unit/core/States.js
@@ -0,0 +1,70 @@
+import { States } from '../../../src/core/States.js';
+
+suite('States', function () {
+  test('initialises with provided state', function () {
+    const s = new States({ fill: 'red', stroke: 'blue' });
+    assert.equal(s.fill, 'red');
+    assert.equal(s.stroke, 'blue');
+  });
+
+  test('setValue() updates the value', function () {
+    const s = new States({ fill: 'red' });
+    s.setValue('fill', 'green');
+    assert.equal(s.fill, 'green');
+  });
+
+  test('setValue() records the original before first modification', function () {
+    const s = new States({ fill: 'red' });
+    s.setValue('fill', 'green');
+    assert.equal(s.getModified().fill, 'red');
+  });
+
+  test('setValue() does not overwrite original on repeated calls', function () {
+    const s = new States({ fill: 'red' });
+    s.setValue('fill', 'green');
+    s.setValue('fill', 'blue');
+    assert.equal(s.getModified().fill, 'red');
+  });
+
+  test('takeDiff() returns the modified map', function () {
+    const s = new States({ fill: 'red' });
+    s.setValue('fill', 'green');
+    const diff = s.takeDiff();
+    assert.equal(diff.fill, 'red');
+  });
+
+  test('takeDiff() clears #modified after returning', function () {
+    const s = new States({ fill: 'red' });
+    s.setValue('fill', 'green');
+    s.takeDiff();
+    assert.deepEqual(s.takeDiff(), {});
+  });
+
+  test('applyDiff() undoes current modifications and replaces #modified', function () {
+    const s = new States({ fill: 'red' });
+    s.setValue('fill', 'green');
+    const outerModified = {};
+    s.applyDiff(outerModified);
+    assert.equal(s.fill, 'red');
+    assert.deepEqual(s.getModified(), {});
+  });
+
+  test('applyDiff() with a non-empty prevModified replaces #modified', function () {
+    const s = new States({ fill: 'red', stroke: 'black' });
+    s.setValue('fill', 'green');
+    const outerModified = { stroke: 'black' };
+    s.applyDiff(outerModified);
+    assert.equal(s.fill, 'red');
+    assert.deepEqual(s.getModified(), { stroke: 'black' });
+  });
+
+  test('push/pop cycle: applyDiff restores prior state', function () {
+    const s = new States({ fill: 'red' });
+    const beforePush = s.takeDiff();
+    s.setValue('fill', 'green');
+    assert.equal(s.fill, 'green');
+    s.applyDiff(beforePush);
+    assert.equal(s.fill, 'red');
+    assert.deepEqual(s.getModified(), {});
+  });
+});
\ No newline at end of file