Determine if two arrays are equal using Jest

Question

Determine if two arrays are equal using Jest

I have a method in the test.ts file:

public async listComponentsDiffer(lastTag: string, workDir: string): Promise<any[]>

This method returns an array with data like this:

[{ components: "toto", newVersion: "2", oldVersion: "1" }]

I am attempting to use Jest to test this method:

test("correct array format", () => {
    // Given
    const lastag = "";
    const workDir = ".";

    // When
    const result = ComponentsService.listComponentsDiffer(lastag, workDir);

    // Then
    const expected = [{ components: "toto", newVersion: "2", oldVersion: "1" }];
    expect(result).toBe(expected);
});

However, I am encountering the following error:

TypeError: test_1.test.listComponentsDiffer is not a function in Jest

How can I properly run my test?

javascript typescript unit-testing jestjs

Answer 1

Answer №1

Make sure to call this method from an instance of the class as it is not a static method.
If you are using async/await syntax, don't forget to include async/await in your test case as well.
Instead of using .toBe, consider using .toEqual for proper comparison.

Use .toEqual for deep equality comparison of object instances.

For example:

test.ts:

export class ComponentsService {
  public async listComponentsDifferent(lastTag: string, workDir: string): Promise<any[]> {
    return [{ components: 'toto', newVersion: '2', oldVersion: '1' }];
  }
}

test.test.ts:

import { ComponentsService } from './test';

describe('12345678', () => {
  test('checking correct array form', async () => {
    const lastag = '';
    const workDir = '.';
    const instance = new ComponentsService();

    const result = await instance.listComponentsDifferent(lastag, workDir);

    const expected = [{ components: 'toto', newVersion: '2', oldVersion: '1' }];
    expect(result).toEqual(expected);
  });
});

Results of unit tests:

 PASS  stackoverflow/12345678/test.test.ts (7.968s)
  12345678
    ✓ checking correct array form (6ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        9.014s

Answer 2

Make sure to call this method from an instance of the class as it is not a static method.
If you are using async/await syntax, don't forget to include async/await in your test case as well.
Instead of using .toBe, consider using .toEqual for proper comparison.

Use .toEqual for deep equality comparison of object instances.

For example:

test.ts:

export class ComponentsService {
  public async listComponentsDifferent(lastTag: string, workDir: string): Promise<any[]> {
    return [{ components: 'toto', newVersion: '2', oldVersion: '1' }];
  }
}

test.test.ts:

import { ComponentsService } from './test';

describe('12345678', () => {
  test('checking correct array form', async () => {
    const lastag = '';
    const workDir = '.';
    const instance = new ComponentsService();

    const result = await instance.listComponentsDifferent(lastag, workDir);

    const expected = [{ components: 'toto', newVersion: '2', oldVersion: '1' }];
    expect(result).toEqual(expected);
  });
});

Results of unit tests:

 PASS  stackoverflow/12345678/test.test.ts (7.968s)
  12345678
    ✓ checking correct array form (6ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        9.014s

Determine if two arrays are equal using Jest

Answer №1

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