diff --git a/packages/svelte/tests/runtime-runes/samples/production/_config.js b/packages/svelte/tests/runtime-runes/samples/production/_config.js
new file mode 100644
index 000000000000..ce36c9d95b06
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/production/_config.js
@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	production: true
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/production/main.svelte b/packages/svelte/tests/runtime-runes/samples/production/main.svelte
new file mode 100644
index 000000000000..d9cff745d15a
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/production/main.svelte
@@ -0,0 +1,7 @@
+<script>
+    import { DEV } from "esm-env";
+
+    if (DEV) {
+        throw new Error("Dev-only code must not run");
+    }
+</script>
\ No newline at end of file
diff --git a/packages/svelte/tests/suite.ts b/packages/svelte/tests/suite.ts
index bbd252b8e188..72c40f526bc1 100644
--- a/packages/svelte/tests/suite.ts
+++ b/packages/svelte/tests/suite.ts
@@ -1,9 +1,11 @@
 import fs from 'node:fs';
-import { it } from 'vitest';
+import { it, vi } from 'vitest';
 
 export interface BaseTest {
 	skip?: boolean;
 	solo?: boolean;
+	/** Set `DEV` to `false` */
+	production?: boolean;
 }
 
 /**
@@ -27,11 +29,31 @@ export function suite<Test extends BaseTest>(fn: (config: Test, test_dir: string
 	return {
 		test: (config: Test) => config,
 		run: async (cwd: string, samples_dir = 'samples') => {
+			const production_tests: Array<[Function, string, Function]> = [];
+
 			await for_each_dir<Test>(cwd, samples_dir, (config, dir) => {
 				let it_fn = config.skip ? it.skip : config.solo ? it.only : it;
 
-				it_fn(dir, () => fn(config, `${cwd}/${samples_dir}/${dir}`));
+				if (config.production) {
+					production_tests.push([it_fn, dir, () => fn(config, `${cwd}/${samples_dir}/${dir}`)]);
+				} else {
+					it_fn(dir, () => fn(config, `${cwd}/${samples_dir}/${dir}`));
+				}
 			});
+
+			let mocked = false;
+			for (const [it, name, test] of production_tests) {
+				it(name, () => {
+					if (!mocked) {
+						vi.doMock('esm-env', async (importEnv) => ({
+							...(await importEnv()),
+							DEV: false
+						}));
+						mocked = true;
+					}
+					return test();
+				});
+			}
 		}
 	};
 }
@@ -45,6 +67,8 @@ export function suite_with_variants<Test extends BaseTest, Variants extends stri
 	return {
 		test: (config: Test) => config,
 		run: async (cwd: string, samples_dir = 'samples') => {
+			const production_tests: Array<[Function, string, Function]> = [];
+
 			await for_each_dir<Test>(cwd, samples_dir, (config, dir) => {
 				let called_common = false;
 				let common: any = undefined;
@@ -57,15 +81,35 @@ export function suite_with_variants<Test extends BaseTest, Variants extends stri
 					const solo = config.solo;
 					let it_fn = skip ? it.skip : solo ? it.only : it;
 
-					it_fn(`${dir} (${variant})`, async () => {
+					const test = async () => {
 						if (!called_common) {
 							called_common = true;
 							common = await common_setup(config, `${cwd}/${samples_dir}/${dir}`);
 						}
 						return fn(config, `${cwd}/${samples_dir}/${dir}`, variant, common);
-					});
+					};
+
+					if (config.production) {
+						production_tests.push([it_fn, `${dir} (${variant})`, test]);
+					} else {
+						it_fn(`${dir} (${variant})`, test);
+					}
 				}
 			});
+
+			let mocked = false;
+			for (const [it, name, test] of production_tests) {
+				it(name, () => {
+					if (!mocked) {
+						vi.doMock('esm-env', async (importEnv) => ({
+							...(await importEnv()),
+							DEV: false
+						}));
+						mocked = true;
+					}
+					return test();
+				});
+			}
 		}
 	};
 }
@@ -108,3 +152,17 @@ export function assert_ok(value: any): asserts value {
 		throw new Error(`Expected truthy value, got ${value}`);
 	}
 }
+
+function run_in_production(fn: (...args: any[]) => void | Promise<void>) {
+	return async (...args: any[]) => {
+		vi.doMock('esm-env', async (importEnv) => ({
+			...(await importEnv()),
+			DEV: false
+		}));
+		try {
+			await fn(...args);
+		} finally {
+			vi.doUnmock('esm-env');
+		}
+	};
+}