# Mark a test as a "todo" with the Bun test runner (/guides/test/todo-tests)

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Related: [Run your tests with the Bun test runner](/guides/test/run-tests.md), [Run tests in watch mode with Bun](/guides/test/watch-mode.md), [Migrate from Jest to Bun's test runner](/guides/test/migrate-from-jest.md), [Mock functions in `bun test`](/guides/test/mock-functions.md), [Spy on methods in `bun test`](/guides/test/spy-on.md), [Set the system time in Bun's test runner](/guides/test/mock-clock.md)

To remind yourself to write a test later, use the `test.todo` function. An implementation isn't required.

```ts icon="/icons/typescript.svg" title="test.test.ts"
import { test } from "bun:test";

// write this later
test.todo("parses durations like 1h30m");
```

***

The `bun test` output reports the number of `todo` tests.

```sh icon="terminal" title="terminal" terminal
bun test
```

```txt
test.test.ts:
✎ parses durations like 1h30m

 0 pass
 1 todo
 0 fail
Ran 1 test across 1 file. [6.00ms]
```

***

You can also write the test before the code it tests exists. Here `parseDuration` is still a stub, and the todo test records what it should eventually do. `bun test` reports this test as `todo` too, without running its body.

```ts icon="/icons/typescript.svg" title="test.test.ts"
import { test, expect } from "bun:test";

// Not written yet; the todo test below says what it should do.
function parseDuration(input: string): number {
  throw new Error("not implemented");
}

test.todo("parses durations like 1h30m", () => {
  expect(parseDuration("1h30m")).toBe(5400);
});
```

***

Pass `--todo` to run the bodies of todo tests. A todo test is *expected to fail*: while `parseDuration` is unimplemented, Bun prints the error, still counts the test as `todo`, and exits with code `0`.

```sh icon="terminal" title="terminal" terminal
bun test --todo
```

```txt
test.test.ts:
1 | import { test, expect } from "bun:test";
2 |
3 | // Not written yet; the todo test below says what it should do.
4 | function parseDuration(input: string): number {
5 |   throw new Error("not implemented");
                                       ^
error: not implemented
      at parseDuration (/path/to/test.test.ts:5:36)
      at <anonymous> (/path/to/test.test.ts:9:10)
✎ parses durations like 1h30m [0.16ms]

 0 pass
 1 todo
 0 fail
Ran 1 test across 1 file. [5.00ms]
```

***

Once you implement `parseDuration` and the body passes, `bun test --todo` reports the test as a failure and exits with a non-zero code. That is the signal to remove `.todo` and turn it into a regular test.

```txt
test.test.ts:
✗ parses durations like 1h30m [0.19ms]
  ^ this test is marked as todo but passes. Remove `.todo` if tested behavior now works

 0 pass
 1 fail
 1 expect() calls
Ran 1 test across 1 file. [5.00ms]
$ echo $?
1 # this is the exit code of the previous command
```

***

See also:

* [Skip a test](/guides/test/skip-tests)
* [Writing tests](/test/writing-tests)