Had a quick look into that mongo memory server and it pull the real mongodb instance for testing so it’s solid. MontyDB in other hand is only a tiny in-completed replica (only had basic CRUD implemented, no aggregation and other fancy stuff).
Could be used for a quick demo for application that requires MongoDB, which was part of my initiative back then.
> Could be used for a quick demo for application that requires MongoDB
If the demo or production only requires those basic operations of course. Those implemented ops are testing against to real MongoDB, so should be good enough for basic usage.
IMO unit tests can be done against any implementation, even a mock one, so using Monty would be beneficial, if it supports all you need.
However, you need to have integration tests, to ensure that such implementation behaves the same as the MongoDB version you have in the production. Such tests only need to be run when you change the implementation or upgrade production MongoDB.
All of the logic in the driver can be unit tested. Actually talking to the back end is functional testing.
It's a common mistake that people think that HTTP implementations can't be unit tested too, but the truth is a bit more complicated. These libraries are essentially a wire protocol and people think of them as 'wire-protocol' instead of 'wire, protocol'. If you think of it instead as a codec with IO, then you write the codec separately and you can fully test the codec without mocking any IO at all.
It's nearly tautological that code that is written to be unit tested can be unit tested, and code that isn't cannot be. And because people want to get their code 'working' and then prove that it works, they are battling uphill to get good tests written, because good tests can't be written. And then some people use this as confirmation bias for why they shouldn't have to write tests.
You can’t test the logic without the parts that interpret the logic. Your mock will fail if I change the name of a alias in my query. A database won’t.
I hope you realize there's a fuzzy line between those, when you have ideal test doubles, that behave like the real thing, but are just configurable in-memory replicas of the dependency.
People get suck a kick out of categorizing their tests, I honestly find that funny.
Can you run it easily before you commit code to a unit, without a dedicated setup? Yes, then it's a unit test to me.
If it was me I wouldn't call it "something" test at all. It's just automated tests. The rest is mostly BS.
If a unit test fails under those circumstances you have little assurance before investigating that changes to your unit caused the failure.
If you have to test scenarios in which other dependencies are needed, then you must move up the testing pyramid. That serves to put in check the expectations of what each type of test should accomplish, and when to execute those tests.
Had a quick look into that mongo memory server and it pull the real mongodb instance for testing so it’s solid. MontyDB in other hand is only a tiny in-completed replica (only had basic CRUD implemented, no aggregation and other fancy stuff).
Could be used for a quick demo for application that requires MongoDB, which was part of my initiative back then.