How to use MemoryDatabase? (for testing purpose)

[Odonno]

Checks before posting an issue

• I have read all the library's documentation (README, CHANGELOG, MIGRATION and /docs)
• I understand I am writing to a human being, doing this open source project on his free time
• I will be involved in my own issue, by answering questions and informing if the issue is resolved

Configuration

• @ngx-pwa/local-storage version: 11.1.0
• Angular version (ng version):

Angular CLI: 11.1.1
Node: 12.18.3
OS: win32 x64

Angular: 11.1.0
... animations, common, compiler, compiler-cli, core, forms
... language-service, localize, platform-browser
... platform-browser-dynamic, router, service-worker
Ivy Workspace: Yes

Package                         Version
---------------------------------------------------------
@angular-devkit/architect       0.1100.7
@angular-devkit/build-angular   0.1100.7
@angular-devkit/core            11.1.1
@angular-devkit/schematics      11.1.1
@angular/cdk                    11.0.3
@angular/cli                    11.1.1
@angular/fire                   6.1.4
@angular/material               11.0.3
@schematics/angular             11.1.1
@schematics/update              0.1101.1
rxjs                            6.6.3
typescript                      4.0.5

Description of the issue

How to use MemoryDatabase? (for testing purpose)

I would like to use an in-memory database to be able to write unit tests in my Angular app.

[cyrilletuzi]

Hi,

The MemoryDatabase is an automatic fallback when indexedDb or localStorage are not available.

So either indexedDb or localStorage is available in the context of your unit tests (which should be the case as unit tests are run in browsers), so there should be no problem, or MemoryDatabase will be used automatically.

Why do you want to disable the normal behavior of the lib?

[Odonno]

I would like to inject a MemoryStorage inside the TestBed so I can control what's inside the storage. You could provide something like the HttpClientTestingModule using the same pattern. What do you think?

Like providing a StorageTestingModule.

[cyrilletuzi]

Like providing a StorageTestingModule.

It could be a possibility.

Another possibility would be to export the different databases type (so MemoryDatabase among them) as public, so you would be able to override LocalDabatabase via NgModule providers (note that you can already do so with your own implementation, or by copying the MemoryDatabase class).

But first I would like to be sure to understand your goal / use case, because it's not clear to me yet.

"control what's inside the storage"

Why not control the real storage directly?

You could provide something like the HttpClientTestingModule using the same pattern.

The HttpClientTestingModule makes sense because during unit tests, the API is not accessible. But the storage is.

[Odonno]

Ok, nevermind. I managed to make Jest functions and it is enough for my needs.