Jest Snippets

Unit Testing Functions

• A big part of testing is understanding how to actually use the function. One tricky part about testing functions, even simple ones, built on-top of libraries that you don't understand is that you need to read these docs and learn.
• Here is an example with a basic Yup schema and then how I tested it:

import { object, string } from 'yup';

const emailSchema = object().shape({
  email: string()
    .trim()
    .email('Email must be a valid format.')
    .required(`You must have an email to register.`),
});

export default emailSchema;

• There are a few things I did of note:
  • first, the validate() function is async so I had to use await to get the result
  • second, I had to use abortEarly: false to get all the errors back. See here for more info
  • third, I used err: any to satisfy TypeScript
  • fourth, I don't usually use try-catching in my tests but I had to here to get the errors back. I'm not sure if there is a better way to do this.
  • fifth, if needed, just console.log the response to see how it works. For the valid email example, I just did console.log(validationResult) to see what it returned

import emailSchema from './emailSchema';

describe('emailSchema', () => {
  it('should require an email', async () => {
    const badInput = { email: '' };
    try {
      await emailSchema.validate(badInput, { abortEarly: false });
    } catch (err: any) {
      expect(err.errors.length).toBe(1);
    }
  });

  it('should require a valid email', async () => {
    const badInput = { email: 'invalidemail' };
    try {
      await emailSchema.validate(badInput, { abortEarly: false });
    } catch (err: any) {
      expect(err.errors).toEqual(['Email must be a valid format.']);
    }
  });

  it('should allow valid email formats', async () => {
    const goodInput = { email: 'valid@example.com' };
    const validationResult = await emailSchema.validate(goodInput, { abortEarly: false });
    expect(validationResult).toEqual(goodInput);
  });
});

[↑] Back to top