jest/no-untyped-mock-factory Style
What it does
This rule triggers a warning if mock() or doMock() is used without a generic type parameter or return type.
Why is this bad?
By default, jest.mock and jest.doMock allow any type to be returned by a mock factory. A generic type parameter can be used to enforce that the factory returns an object with the same shape as the original module, or some other strict type. Requiring a type makes it easier to use TypeScript to catch changes needed in test mocks when the source module changes.
Example
// invalid
typescript
jest.mock("../moduleName", () => {
return jest.fn(() => 42);
});
jest.mock("./module", () => ({
...jest.requireActual("./module"),
foo: jest.fn(),
}));
jest.mock("random-num", () => {
return jest.fn(() => 42);
});// valid
typescript
// Uses typeof import()
jest.mock<typeof import("../moduleName")>("../moduleName", () => {
return jest.fn(() => 42);
});
jest.mock<typeof import("./module")>("./module", () => ({
...jest.requireActual("./module"),
foo: jest.fn(),
}));
// Uses custom type
jest.mock<() => number>("random-num", () => {
return jest.fn(() => 42);
});
// No factory
jest.mock("random-num");
// Virtual mock
jest.mock(
"../moduleName",
() => {
return jest.fn(() => 42);
},
{ virtual: true },
);