Writing a Node CLI in my module I have a console.log with chalk, example:
console.log(
chalk.green(`${delta}:`),
chalk.white(`\nAPI: ${apiPath}`),
)
when I run a Jest code coverage --coverage I'm reminded that I didn't have a test so I wrote:
test(`Test console log`, async () => {
await mod(params)
await expect(console.log).toBe(`${delta}:\nAPI: ${apiPath}`)
})
but I get an error of:
Expected: "string"
Received: [Function log]
Second attempt from research I tried:
test(`Test console log`, async () => {
await mod(params)
await expect(console.log).toHaveBeenCalledWith(`${delta}:\nAPI: ${apiPath}`)
})
but I get an error of:
Received has type: function
Received has value: [Function log]
Research:
With Jest how can I test a console.log that uses chalk?
// newTest.js
const chalk = require('chalk');
function functionUnderTest() {
console.log(chalk.green(`${delta}:`), chalk.white(`\nAPI: ${apiPath}`));
}
module.exports = functionUnderTest;
// newTest.test.js
const functionUnderTest = require('./newTest');
const chalk = require('chalk');
jest.mock('chalk', () => ({
green: jest.fn(),
white: jest.fn(),
}));
it('calls console.log and chalk.blue with correct arguments', () => {
const spy = jest.spyOn(global.console, 'log');
chalk.green.mockReturnValueOnce('test-blue');
chalk.white.mockReturnValueOnce('test-white');
functionUnderTest(5, 'my-path');
expect(chalk.green).toHaveBeenCalledWith('5:');
expect(chalk.white).toHaveBeenCalledWith('\nAPI: my-path');
expect(global.console.log).toHaveBeenCalledWith('test-blue', 'test-white');
spy.mockRestore();
});
To access global objects you have to use global context (Jest: how to mock console when it is used by a third-party-library?).
You do that by spying log method of the console global object.
The important part regarding the test itself is that there are 2 dependencies that need to be mocked, the console.log (which is done in the spy) and the chalk (which i'm doing with the jest.mock) where i say that it has a property named green which is a mocked function (and white). Here what should be tested is that the console.log prints what is returned from the chalk.green call. So assigned a dummy string to be the result of the chalk.green call (test-result) and assert that console.log is called with that same string. The same for the white mock function.