Dynamically generate test cases with Jest

As long as you know which cases you want to test up-front (for example, you're not trying to generate them after a network request) you can use Jest to batch out multiple cases at once.

The syntax looks like this

test.each([])('test name', () => {})

Single argument per test

If you use the wildcard %s in your test name, it will inject the first string in your test case. The following test spec will generate five different tests.

1test.each([
2  'FULL_TIME',
3  'PART_TIME',
4  'SELF_EMPLOYED',
5  'UNEMPLOYED',
6  'RETIRED',
7])('can set employment type to %s', (type) => {
8
9  // Test content here
10}),
11

1test('can set employment type to FULL_TIME', () => {
2  const type = 'FULL_TIME'
3
4  // Test content here
5})
6
7test('can set employment type to PART_TIME', () => {
8  const type = 'PART_TIME'
9
10  // Test content here
11})
12
13test('can set employment type to SELF_EMPLOYED', () => {
14  const type = 'SELF_EMPLOYED'
15
16  // Test content here
17})
18
19test('can set employment type to UNEMPLOYED', () => {
20  const type = 'UNEMPLOYED'
21
22  // Test content here
23})
24
25test('can set employment type to RETIRED', () => {
26  const type = 'RETIRED'
27
28  // Test content here
29})
30

Multiple arguments per test

Each item in the array can itself be an array of arguments.

In the test name, you can use %s multiple times in order to print out the argument.

1test.each([
2  ['FULL_TIME', 'FULL_TIME'],
3  ['FULL_TIME', 'PART_TIME'],
4  ['FULL_TIME', 'SELF_EMPLOYED'],
5  ['FULL_TIME', 'UNEMPLOYED'],
6  ['FULL_TIME', 'RETIRED'],
7  ['PART_TIME', 'FULL_TIME'],
8  ['PART_TIME', 'PART_TIME'],
9  ['PART_TIME', 'SELF_EMPLOYED'],
10  ['PART_TIME', 'UNEMPLOYED'],
11  ['PART_TIME', 'RETIRED'],
12  ['SELF_EMPLOYED', 'FULL_TIME'],
13  ['SELF_EMPLOYED', 'PART_TIME'],
14  ['SELF_EMPLOYED', 'SELF_EMPLOYED'],
15  ['SELF_EMPLOYED', 'UNEMPLOYED'],
16  ['SELF_EMPLOYED', 'RETIRED'],
17  ['UNEMPLOYED', 'FULL_TIME'],
18  ['UNEMPLOYED', 'PART_TIME'],
19  ['UNEMPLOYED', 'SELF_EMPLOYED'],
20  ['UNEMPLOYED', 'UNEMPLOYED'],
21  ['UNEMPLOYED', 'RETIRED'],
22  ['RETIRED', 'FULL_TIME'],
23  ['RETIRED', 'PART_TIME'],
24  ['RETIRED', 'SELF_EMPLOYED'],
25  ['RETIRED', 'UNEMPLOYED'],
26  ['RETIRED', 'RETIRED'],
27])('can set employment type from %s to %s', ([ firstType, secondType ]) => {
28
29  // Test content here
30}),
31

1test('can set employment type from FULL_TIME to FULL_TIME', () => {
2  const firstType = 'FULL_TIME'
3  const secondType = 'FULL_TIME'
4
5  // Test content here
6})
7
8test('can set employment type from FULL_TIME to PART_TIME', () => {
9  const firstType = 'FULL_TIME'
10  const secondType = 'PART_TIME'
11
12  // Test content here
13})
14
15test('can set employment type from FULL_TIME to SELF_EMPLOYED', () => {
16  const firstType = 'FULL_TIME'
17  const secondType = 'SELF_EMPLOYED'
18
19  // Test content here
20})
21
22// …and so on 22 more times
23