How to write unit tests for validator?

[durianwaffle]

I am writing unit test for validator in langium.
I am wondering how do I pass the validationAcceptor into my validationFunction checkAssignmentType. Any example on it?
I saw a similar example but still not clear how to text validator since there all my validationFunctions return void type.

https://github.com/eclipse-langium/langium/blob/main/examples/requirements/src/language-server/tests-lang-validator.ts

[msujew]

Hey @durianwaffle,

we export expectError, expectIssue, expectNoIssues, expectWarning, validationHelper from langium/test that should help you to write validation tests. See also our own validation tests:

https://github.com/eclipse-langium/langium/blob/main/packages/langium/test/grammar/grammar-validator.test.ts

[msujew]

You can inject services in your MyDSLValidator class constructor.

[msujew]

I really cannot follow. What do you want to achieve? Can you show some (pseudo)-code for what you want to do?

[durianwaffle]

I still face issues using validationHelper to inject my own services. I have injected services in each constructor of each of my services and validator.
So, I used constructor to new a validator and check the content of ValidationAcceptor in it.
But I found that if I use expect(mockValidationAcceptor).toHaveBeenCalledWith('error', 'This is an error message', expect.anything()), there will be JS out of memory issue. Then I used expect(mockValidationAcceptor).toHaveBeenCalledTimes(1); which works. But even when it doesn't have validation error the mockValidationAcceptor will be called

[msujew]

How do you create the mockValidationAcceptor?

[durianwaffle]

I created a mockValidationAcceptor like the one shown below.

mockValidationAcceptor = vi.fn(
        <N extends AstNode>(
            severity: 'error' | 'warning' | 'info' | 'hint',
            message: string,
            info: DiagnosticInfo<N>
        ) => {
            return message;
        }
    )

But now I know that I should use the code below instead in beforeAll. It will work.

const acceptor = () => null;
toSpyOn = {
    acceptor
};
acceptorSpy = vitest.spyOn(toSpyOn, 'acceptor');
validator = new MyDSLValidator(aService, bService);
validatorAny = validator as any;
validatorAny['checkFeatureCallArguments'](featureCall, toSpyOn.acceptor);

And always use acceptorSpy.mockClear(); in each test to make sure the call times is not accumulated.