CODEWITHSUNDEEP
javascriptjasmine
Yaniv
Yaniv

Reputation: 391

Jasmine custom matchers and before all

When using Jasmine, is there a difference between adding a matcher in a beforeAll block vs a beforeEach block?

As far as I can tell, it works both ways. However, every documentation/tutorial I find online uses beforeEach. Is this simply because Jasmine's built-in beforeAll block is a relatively new feature, or is it avoided due to a potential pitfall when running the tests?

Using beforeAll makes more sense to me (why add the same matcher more than once?), but I'd like to make sure that I'm not exposing my tests to any problems.

Upvotes: 4

Views: 284

Answers (1)

Joseph238
Joseph238

Reputation: 1224

There are two differences - 1) the execution order, and 2) the scope in which the change is persistent. I've spent many hours testing in Jasmine at work and the differences between beforeAll and beforeEach have always behaved as they should (well, except one bug I helped them fix). The only reason I've found to use beforeEach instead of beforeAll is to avoid test pollution. This isn't an issue for custom matchers, so it should be just fine to go ahead and use beforeAll.

Execution order - in any given describe block, order is as follows:

  • its beforeAll
  • its beforeEach
  • its first nested it or describe block (including their setups and teardowns)
  • its afterEach
  • for each additional nested it or describe block, repeat the last three steps
  • its afterAll

I've confirmed this through testing and sources like this.

Scope - Any added variables, properties on the this keyword, spies, or custom matchers (as mentioned), will be persistent and accessible in the given block, throughout the block (including in nested blocks), as soon as the code that adds them has been executed. For example, if I set this.foo in the beforeAll of a describe, it can be accessed in that describe's beforeEach, afterEach, afterAll, and it and describe blocks. As soon as I leave the describe block, this.foo will no longer be accessible.

Upvotes: 2

Related Questions