diff --git a/packages/bun-polyfills/src/modules/test.ts b/packages/bun-polyfills/src/modules/test.ts
new file mode 100644
index 0000000000..79f35f5023
--- /dev/null
+++ b/packages/bun-polyfills/src/modules/test.ts
@@ -0,0 +1,137 @@
+import _dateFormat from 'dateformat';
+const dateFormat = _dateFormat as unknown as typeof import('dateformat').default; // 10/10 types :D
+import { expect as jestexpect } from 'expect';
+import _jesteach from 'jest-each';
+const jesteach = _jesteach.default as unknown as typeof import('jest-each').default; // bad types, again...
+import * as jestmock from 'jest-mock';
+import nodetest from 'node:test';
+import chp from 'node:child_process';
+import { promisify } from 'node:util';
+import type { Mock } from 'bun:test';
+const exec = promisify(chp.exec);
+
+const bunmock: typeof import('bun:test')['mock'] = function mock(fn) {
+    return jestmock.fn(fn);
+};
+bunmock.module = (id, factory) => { }; // TODO: Need to integrate this with the ESM loader somehow.
+bunmock.restore = () => { }; // TODO
+
+const bundescribe: typeof import('bun:test')['describe'] = (name, fn) => nodetest.describe(name, fn);
+bundescribe.only = (name, fn) => nodetest.describe.only(name, fn);
+bundescribe.todo = (name, fn) => nodetest.describe.todo(name, fn);
+bundescribe.skip = (name, fn) => nodetest.describe.skip(name, fn);
+bundescribe.skipIf = (condition) => condition ? nodetest.describe.skip : nodetest.describe;
+bundescribe.if = (condition) => condition ? nodetest.describe : () => void 0;
+bundescribe.each = (table: any) => {
+    return (title: string, suite: AnyFunction) => jesteach(table).describe(title, suite);
+};
+
+const bunExpect = jestexpect as unknown as typeof import('bun:test')['expect'];
+bunExpect.unreachable = (msg) => {
+    if (msg instanceof Error) throw msg;
+    else throw new Error(msg ?? 'Unreachable code reached');
+};
+
+const bunit: typeof import('bun:test')['it'] = (name, fn) => {
+    nodetest.it(name, fn.length ? async (t, done) => void await fn(done) : async (t) => void await (fn as () => Promise<void>)());
+};
+bunit.only = (name, fn) => nodetest.only(name, fn.length ? async (t, done) => void await fn(done) : async (t) => void await (fn as () => Promise<void>)());
+bunit.todo = (name, fn) => nodetest.todo(name, fn?.length ? async (t, done) => void await fn?.(done) : async (t) => void await (fn as () => Promise<void>)());
+bunit.skip = (name, fn) => nodetest.skip(name, fn.length ? async (t, done) => void await fn(done) : async (t) => void await (fn as () => Promise<void>)());
+bunit.if = (condition) => condition ? bunit : () => void 0;
+bunit.skipIf = (condition) => condition ? bunit.skip : bunit;
+bunit.each = (table: any) => {
+    return (title: string, test: AnyFunction) => jesteach(table).it(title, test);
+};
+
+const testModule = {
+    // This entire function is overall very hacky and little tested for now.
+    // Maybe it would be better to just monkeypatch the relevant JS apis instead?
+    setSystemTime(now?: Date | number) {
+        if (process.platform === 'linux') {
+            const sudo = ''; // process.getuid?.() === 0 ? '' : 'sudo ';
+            if (typeof now === 'undefined') {
+                exec(`${sudo}timedatectl set-ntp true`);
+                return this;
+            }
+            //? Doesn't work on non-systemd distros, nor WSL by default...
+            exec(
+                `${sudo}timedatectl set-ntp false && ` +
+                `${sudo}date -s "${dateFormat(now, "UTC:mm/dd/yyyy HH:MM:ss")}" --utc && ` +
+                `${sudo}hwclock -w --utc`
+            );
+        } else if (process.platform === 'win32') {
+            const Win32DateFormat = (() => {
+                try {
+                    const stdout = chp.execSync('date');
+                    return stdout.toString('utf8').match(/Enter the new date: \((.+)\)/)?.[1] ?? 'dd-mm-yy';
+                } catch (e) {
+                    const err = e as { stdout: Buffer; };
+                    return err.stdout.toString('utf8').match(/Enter the new date: \((.+)\)/)?.[1] ?? 'dd-mm-yy';
+                }
+            })();
+            if (typeof now === 'undefined') {
+                // TODO: How to reset system time on Windows? Below might work but is messy and needs admin...
+                /* net stop w32time
+                   w32tm /unregister
+                   w32tm /register
+                   net start w32time
+                   w32tm /resync */
+                return this;
+            }
+            exec(
+                `date ${dateFormat(now, Win32DateFormat)} && ` +
+                `time ${dateFormat(now, "HH:MM:ss")}`
+            );
+        } else throw new Error(`Unsupported platform for setSystemTime: ${process.platform}`); // TODO: How to set system time on MacOS? Can't test for now :(
+        return this;
+    },
+    spyOn<T extends object, K extends keyof T>(obj: T, methodOrPropertyValue: K): Mock<T[K] extends AnyFunction ? T[K] : never> {
+        const mock = jestmock.spyOn(
+            obj,
+            // @ts-expect-error jest has a really convoluted type for this that isnt worth trying to replicate
+            methodOrPropertyValue,
+        ) as jestmock.Spied<any>;
+        // @ts-expect-error same reason as above
+        return mock;
+    },
+    beforeAll(fn) {
+        nodetest.before(fn.length ? (s, done) => void fn(done) : (s) => void (fn as () => void)());
+    },
+    beforeEach(fn) {
+        nodetest.beforeEach(fn.length ? (s, done) => void fn(done) : (s) => void (fn as () => void)());
+    },
+    afterAll(fn) {
+        nodetest.after(fn.length ? (s, done) => void fn(done) : (s) => void (fn as () => void)());
+    },
+    afterEach(fn) {
+        nodetest.afterEach(fn.length ? (s, done) => void fn(done) : (s) => void (fn as () => void)());
+    },
+    mock: bunmock,
+    jest: {
+        restoreAllMocks() {
+            bunmock.restore();
+        },
+        fn(func) {
+            return jestmock.fn(func);
+        },
+    },
+    describe: bundescribe,
+    test: bunit,
+    it: bunit,
+    expect: bunExpect, // TODO: this is not fully compatible, needs finer grained implementation
+} satisfies typeof import('bun:test');
+
+export const setSystemTime = testModule.setSystemTime;
+export const spyOn = testModule.spyOn;
+export const beforeAll = testModule.beforeAll;
+export const beforeEach = testModule.beforeEach;
+export const afterAll = testModule.afterAll;
+export const afterEach = testModule.afterEach;
+export const mock = testModule.mock;
+export const jest = testModule.jest;
+export const describe = testModule.describe;
+export const test = testModule.test;
+export const it = testModule.it;
+export const expect = testModule.expect;
+export default testModule;