I like to use Javascript as a replacement for bash scripts.
Assuming a contrived script called start.js that is run using node start.js
:
const shelljs = require("shelljs")
if (!shelljs.which("serve")) {
shelljs.echo("'serve' is missing, please run 'npm ci'")
process.exit(1)
}
shelljs.exec("serve -s build -l 3000")
How do I test that:
serve
isn't available then serve -s build -l 3000
is never called and program exits with code 1.serve
is available then serve -s build -l 3000
is called.I don't mind mocking "shelljs", process.exit
or anything else.
My main issue is figuring out how to require
or import
such a functionless and moduleless file in a test suite and get it to run once on each separate test with the mocks present without actually turning this into a CommonJS/ES6 module.
Just mock shelljs
module, and spy process.exit
function.
describe("start.js", () => {
let shelljs
let exitSpy
beforeEach(() => {
jest.mock("shelljs", () => {
return {
exec: jest.fn(),
which: jest.fn(),
echo: jest.fn(),
}
})
shelljs = require("shelljs")
exitSpy = jest.spyOn(process, "exit").mockImplementation(() => {})
});
afterEach(() => {
jest.resetModules()
jest.resetAllMocks()
})
it("should execute process.exit with code is 1 when 'serve' is not existed", () => {
shelljs.which.mockReturnValue(false)
require("./start")
expect(shelljs.which).toHaveBeenCalledWith("serve");
expect(shelljs.echo).toHaveBeenCalledWith("'serve' is missing, please run 'npm ci'")
expect(exitSpy).toHaveBeenCalledWith(1)
// expect(shelljs.exec).toHaveBeenCalled() // can not check like that, exitSpy will not "break" your code, it will be work well if you use if/else syntax
});
it("should execute serve when 'serve' is existed", () => {
shelljs.which.mockReturnValue(true)
require("./start")
expect(shelljs.which).toHaveBeenCalledWith("serve");
expect(shelljs.echo).not.toHaveBeenCalled()
expect(exitSpy).not.toHaveBeenCalled()
expect(shelljs.exec).toHaveBeenCalledWith("serve -s build -l 3000")
});
})
Another way to make sure the production code with be break when process.exit
is called. Mock exit
function throw an Error, then expect shelljs.exec
will not be called
describe("start.js", () => {
let shelljs
let exitSpy
beforeEach(() => {
jest.mock("shelljs", () => {
return {
exec: jest.fn(),
which: jest.fn(),
echo: jest.fn(),
}
})
shelljs = require("shelljs")
exitSpy = jest.spyOn(process, "exit").mockImplementation(() => {
throw new Error("Mock");
})
});
afterEach(() => {
jest.resetModules()
jest.resetAllMocks()
})
it("should execute process.exit with code is 1 when 'serve' is not existed", () => {
shelljs.which.mockReturnValue(false)
expect.assertions(5)
try {
require("./start")
} catch (error) {
expect(error.message).toEqual("Mock")
}
expect(shelljs.which).toHaveBeenCalledWith("serve");
expect(shelljs.echo).toHaveBeenCalledWith("'serve' is missing, please run 'npm ci'")
expect(exitSpy).toHaveBeenCalledWith(1)
expect(shelljs.exec).not.toHaveBeenCalled()
});
it("should execute serve when 'serve' is existed", () => {
shelljs.which.mockReturnValue(true)
require("./start")
expect(shelljs.which).toHaveBeenCalledWith("serve");
expect(shelljs.echo).not.toHaveBeenCalled()
expect(exitSpy).not.toHaveBeenCalled()
expect(shelljs.exec).toHaveBeenCalledWith("serve -s build -l 3000")
});
})