mirror of
https://github.com/oven-sh/bun
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96 lines
3.6 KiB
Markdown
96 lines
3.6 KiB
Markdown
Create mocks with the `mock` function.
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```ts
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import { test, expect, mock } from "bun:test";
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const random = mock(() => Math.random());
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test("random", async () => {
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const val = random();
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expect(val).toBeGreaterThan(0);
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expect(random).toHaveBeenCalled();
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expect(random).toHaveBeenCalledTimes(1);
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});
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```
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{% callout %}
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Alternatively, you can use the `jest.fn()` function, as in Jest. It behaves identically.
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```ts
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import { test, expect, jest } from "bun:test";
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const random = jest.fn(() => Math.random());
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test("random", async () => {
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const val = random();
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expect(val).toBeGreaterThan(0);
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expect(random).toHaveBeenCalled();
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expect(random).toHaveBeenCalledTimes(1);
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});
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```
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{% /callout %}
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The result of `mock()` is a new function that's been decorated with some additional properties.
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```ts
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import { mock } from "bun:test";
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const random = mock((multiplier: number) => multiplier * Math.random());
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random(2);
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random(10);
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random.mock.calls;
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// [[ 2 ], [ 10 ]]
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random.mock.results;
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// [
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// { type: "return", value: 0.6533907460954099 },
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// { type: "return", value: 0.6452713933037312 }
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// ]
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```
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The following properties and methods are implemented on mock functions.
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- [x] [mockFn.getMockName()](https://jestjs.io/docs/mock-function-api#mockfngetmockname)
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- [x] [mockFn.mock.calls](https://jestjs.io/docs/mock-function-api#mockfnmockcalls)
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- [x] [mockFn.mock.results](https://jestjs.io/docs/mock-function-api#mockfnmockresults)
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- [x] [mockFn.mock.instances](https://jestjs.io/docs/mock-function-api#mockfnmockinstances)
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- [x] [mockFn.mock.contexts](https://jestjs.io/docs/mock-function-api#mockfnmockcontexts)
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- [x] [mockFn.mock.lastCall](https://jestjs.io/docs/mock-function-api#mockfnmocklastcall)
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- [x] [mockFn.mockClear()](https://jestjs.io/docs/mock-function-api#mockfnmockclear)
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- [x] [mockFn.mockReset()](https://jestjs.io/docs/mock-function-api#mockfnmockreset)
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- [x] [mockFn.mockRestore()](https://jestjs.io/docs/mock-function-api#mockfnmockrestore)
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- [x] [mockFn.mockImplementation(fn)](https://jestjs.io/docs/mock-function-api#mockfnmockimplementationfn)
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- [x] [mockFn.mockImplementationOnce(fn)](https://jestjs.io/docs/mock-function-api#mockfnmockimplementationoncefn)
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- [x] [mockFn.mockName(name)](https://jestjs.io/docs/mock-function-api#mockfnmocknamename)
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- [x] [mockFn.mockReturnThis()](https://jestjs.io/docs/mock-function-api#mockfnmockreturnthis)
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- [x] [mockFn.mockReturnValue(value)](https://jestjs.io/docs/mock-function-api#mockfnmockreturnvaluevalue)
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- [x] [mockFn.mockReturnValueOnce(value)](https://jestjs.io/docs/mock-function-api#mockfnmockreturnvalueoncevalue)
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- [x] [mockFn.mockResolvedValue(value)](https://jestjs.io/docs/mock-function-api#mockfnmockresolvedvaluevalue)
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- [x] [mockFn.mockResolvedValueOnce(value)](https://jestjs.io/docs/mock-function-api#mockfnmockresolvedvalueoncevalue)
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- [x] [mockFn.mockRejectedValue(value)](https://jestjs.io/docs/mock-function-api#mockfnmockrejectedvaluevalue)
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- [x] [mockFn.mockRejectedValueOnce(value)](https://jestjs.io/docs/mock-function-api#mockfnmockrejectedvalueoncevalue)
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- [x] [mockFn.withImplementation(fn, callback)](https://jestjs.io/docs/mock-function-api#mockfnwithimplementationfn-callback)
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## `.spyOn()`
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It's possible to track calls to a function without replacing it with a mock. Use `spyOn()` to create a spy; these spies can be passed to `.toHaveBeenCalled()` and `.toHaveBeenCalledTimes()`.
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```ts
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import { test, expect, spyOn } from "bun:test";
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const ringo = {
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name: "Ringo",
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sayHi() {
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console.log(`Hello I'm ${this.name}`);
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},
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};
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const spy = spyOn(ringo, "sayHi");
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test("spyon", () => {
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expect(spy).toHaveBeenCalledTimes(0);
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ringo.sayHi();
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expect(spy).toHaveBeenCalledTimes(1);
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});
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```
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