From f1400091ff0eed4f490085f2fb5ab5c0903fa96f Mon Sep 17 00:00:00 2001
From: Iwo Plaza <iwoplaza@gmail.com>
Date: Wed, 7 Jan 2026 17:54:26 +0100
Subject: [PATCH 1/2] Update bufferUsage.test.ts

---
 packages/typegpu/tests/bufferUsage.test.ts | 68 ++++++++++++++++++++++
 1 file changed, 68 insertions(+)

diff --git a/packages/typegpu/tests/bufferUsage.test.ts b/packages/typegpu/tests/bufferUsage.test.ts
index 224d4c877c..46a611bc36 100644
--- a/packages/typegpu/tests/bufferUsage.test.ts
+++ b/packages/typegpu/tests/bufferUsage.test.ts
@@ -145,6 +145,40 @@ describe('TgpuBufferMutable', () => {
     `);
   });
 
+  it('cannot be mutated (primitive)', ({ root }) => {
+    const foo = root.createUniform(d.f32);
+
+    const main = () => {
+      'use gpu';
+      foo.$ += 1;
+    };
+
+    expect(tgpu.resolve([main])).toMatchInlineSnapshot(`
+      "@group(0) @binding(0) var<uniform> foo: f32;
+
+      fn main() {
+        foo += 1f;
+      }"
+    `);
+  });
+
+  it('cannot be mutated (non-primitive)', ({ root }) => {
+    const foo = root.createUniform(d.vec3f);
+
+    const main = () => {
+      'use gpu';
+      foo.$.x += 1;
+    };
+
+    expect(tgpu.resolve([main])).toMatchInlineSnapshot(`
+      "@group(0) @binding(0) var<uniform> foo: vec3f;
+
+      fn main() {
+        foo.x += 1f;
+      }"
+    `);
+  });
+
   describe('simulate mode', () => {
     it('allows accessing .$ in simulate mode', ({ root }) => {
       const buffer = root.createBuffer(d.u32, 0).$usage('storage');
@@ -260,6 +294,40 @@ describe('TgpuBufferReadonly', () => {
     `);
   });
 
+  it('cannot be mutated (primitive)', ({ root }) => {
+    const foo = root.createReadonly(d.f32);
+
+    const main = () => {
+      'use gpu';
+      foo.$ += 1;
+    };
+
+    expect(tgpu.resolve([main])).toMatchInlineSnapshot(`
+      "@group(0) @binding(0) var<storage, read> foo: f32;
+
+      fn main() {
+        foo += 1f;
+      }"
+    `);
+  });
+
+  it('cannot be mutated (non-primitive)', ({ root }) => {
+    const foo = root.createReadonly(d.vec3f);
+
+    const main = () => {
+      'use gpu';
+      foo.$.x += 1;
+    };
+
+    expect(tgpu.resolve([main])).toMatchInlineSnapshot(`
+      "@group(0) @binding(0) var<storage, read> foo: vec3f;
+
+      fn main() {
+        foo.x += 1f;
+      }"
+    `);
+  });
+
   describe('simulate mode', () => {
     it('allows accessing .$ in simulate mode', ({ root }) => {
       const buffer = root.createBuffer(d.f32, 123).$usage('storage');

From 5c950498d793c6a7ea5ba37c0b9625f9c8163e66 Mon Sep 17 00:00:00 2001
From: Iwo Plaza <iwoplaza@gmail.com>
Date: Wed, 7 Jan 2026 17:58:26 +0100
Subject: [PATCH 2/2] Failing tests

---
 packages/typegpu/tests/bufferUsage.test.ts | 34 ++++------------------
 1 file changed, 6 insertions(+), 28 deletions(-)

diff --git a/packages/typegpu/tests/bufferUsage.test.ts b/packages/typegpu/tests/bufferUsage.test.ts
index 46a611bc36..ab7c537854 100644
--- a/packages/typegpu/tests/bufferUsage.test.ts
+++ b/packages/typegpu/tests/bufferUsage.test.ts
@@ -150,16 +150,11 @@ describe('TgpuBufferMutable', () => {
 
     const main = () => {
       'use gpu';
+      // @ts-expect-error
       foo.$ += 1;
     };
 
-    expect(tgpu.resolve([main])).toMatchInlineSnapshot(`
-      "@group(0) @binding(0) var<uniform> foo: f32;
-
-      fn main() {
-        foo += 1f;
-      }"
-    `);
+    expect(() => tgpu.resolve([main])).toThrowErrorMatchingInlineSnapshot();
   });
 
   it('cannot be mutated (non-primitive)', ({ root }) => {
@@ -170,13 +165,7 @@ describe('TgpuBufferMutable', () => {
       foo.$.x += 1;
     };
 
-    expect(tgpu.resolve([main])).toMatchInlineSnapshot(`
-      "@group(0) @binding(0) var<uniform> foo: vec3f;
-
-      fn main() {
-        foo.x += 1f;
-      }"
-    `);
+    expect(() => tgpu.resolve([main])).toThrowErrorMatchingInlineSnapshot();
   });
 
   describe('simulate mode', () => {
@@ -299,16 +288,11 @@ describe('TgpuBufferReadonly', () => {
 
     const main = () => {
       'use gpu';
+      // @ts-expect-error
       foo.$ += 1;
     };
 
-    expect(tgpu.resolve([main])).toMatchInlineSnapshot(`
-      "@group(0) @binding(0) var<storage, read> foo: f32;
-
-      fn main() {
-        foo += 1f;
-      }"
-    `);
+    expect(() => tgpu.resolve([main])).toThrowErrorMatchingInlineSnapshot();
   });
 
   it('cannot be mutated (non-primitive)', ({ root }) => {
@@ -319,13 +303,7 @@ describe('TgpuBufferReadonly', () => {
       foo.$.x += 1;
     };
 
-    expect(tgpu.resolve([main])).toMatchInlineSnapshot(`
-      "@group(0) @binding(0) var<storage, read> foo: vec3f;
-
-      fn main() {
-        foo.x += 1f;
-      }"
-    `);
+    expect(() => tgpu.resolve([main])).toThrowErrorMatchingInlineSnapshot();
   });
 
   describe('simulate mode', () => {