generate-test-utils

A Prisma generator to create some utility functions useful for writing unit/integration tests.

Usage

Include the generator in your prisma.schema file:

1generator testUtilGenerator {
2  provider = "prisma-generate-test-utils"
3  output   = "../src"
4}

Then generate using the Prisma cli: prisma generate.

You'll now see some functions in the output file.

Testing Utils

A few utilities useful for testing will be generated for you under {output}/__testing__/prisma-generated.

Mock client

We will generate a mock prisma client that can be used in unit tests in place of the actual client. All methods are stubbed with jest.fn().

Example:

1import { makePrismaClientMock, makeUser } from './__testing/prisma-generated';
2
3test('Test some functionallity', async () => {
4  const mockPrisma = makePrismaClientMock();
5
6  const dummyUser = makeUser();
7
8  mockPrisma.user.findOne.mockReturnValue(dummyUser);
9
10  someFunctionUserTest({ prisma: mockPrisma });
11
12  expect(mockPrisma.user.findOne).toHaveBeenCalledTimes(1);
13});

Seed Functions

For each Model in your Prisma schema we will generate the following functions:

makeX

Where X is the model name, e.g. for a User model this would be makeUser. This function will assemble an object of type X and randomly generate the values based on the types specified in the Prisma schema.

The signature of this function is:

1function makeX(override: Partial<X>): X {}

Example for a User model:

1import { makeUser } from './__testing__/prisma-generated';
2
3// pass no override and all required fields will be randomly generated for you
4const randomUser = makeUser();
5
6// or pass an object to override any values
7const customUser = makeUser({
8  id: 'some-id',
9  name: 'Ellie',
10  // pass any other User fields
11});

seedX

Where X is the model name, e.g. for a User model this would be seedUser. This function will assemble an object of type X and randomly generate the values based on the types specified in the Prisma schema and write it to your Database.

The signature of this function is:

1function seedX(override: Partial<X>): Promise<X> {}

Example for a User model:

1import { seedUser } from './__testing__/prisma-generated';
2
3// pass no override and all required fields will be randomly generated for you
4const randomUser = await seedUser();
5
6// or pass an object to override any values
7const customUser = await seedUser({
8  id: 'some-id',
9  name: 'Ellie',
10  // pass any other User fields
11});

seedNXs

Where X is the model name, e.g. for a User model this would be seedNUsers. This function will assemble n objects of type X and randomly generating different values based on the types specified in the Prisma schema and write all n objects to your Database.

The signature of this function is:

1function seedNXs(n: int, override: Partial<X>): Promise<X[]> {}

Example for a User model:

1import { seedNUsers } from './__testing__/prisma-generated';
2
3// pass no override and all required fields will be randomly generated for you, these fields will be different for each User
4const tenRandomUser = await seedNUsers(10);
5
6// or pass an override to specify values that should be applied to each User
7const tenUsersWithTheSameName = await seedNUsers(10, {
8  name: 'Ellie',
9  // pass any other User fields here
10});
11
12// or pass an override function to specify different values for each {{ name }}
13const tenUsersWithTheDifferentIds = await seedNUsers(10, {
14  id: (index) => `some-id-${index}`,
15});

This can be useful when seeding a bunch of stuff e.g.:

1const facilities = await seedNFacilities(10);
2
3const users = await seedNUsers(10, {
4  facilityId: (i) => facilities[i].id,
5});
6
7// and so on...

deleteSeededXs

Where X is the model name, e.g. for a User model this would be deleteSeededUsers. This function will perform a cascading delete on all records that have been created by the seedX or seedNXs functions generated by this package. This is useful for clearing up after tests.

This works because each of the seed functions adds a seeded_for_test_ prefix to the primary key before writing; we then use this to perform the delete.

This delete is cascading meaning any records in other tables that reference the records being deleted will also be deleted.

Example for a User model:

1import { deleteSeededUsers } from './__testing__/prisma-generated';
2
3// in a test file
4afterEach(async () => {
5  await deleteSeededUsers();
6});

Random Value Generation

Based on the values in your Prisma schema we will randomly generate values for you.

// TODO: Document mapping between Prisma types and random generators when this has stabilised a bit.