review: test: add tests for substitution class

[Rohitesh-Kumar-Jain]

#1818

Hi, I have added 3 new tests for methods of the Substitution class :

1. testSubstituteMethodBody should kill this mutation :

2. testSubstituteStatement should kill this mutation :

3. testSubstituteFieldDefaultExpressionshould kill this mutation :

Link to #3967

[slarse]

Hi @Rohitesh-Kumar-Jain,

These tests are a little bit tell-tale of the "chasing coverage" problem I've mentioned a few times. They don't really test the core functionality of these methods. Your tests are designed to essentially test the methods as getters (as the contracts say). But the substitute methods are not plain getters, but rather as the name implies, they are meant to perform substitutions.

I would urge you to carefully study the templating documentation to get a better idea of what the purpose of these methods is.

It is a bit hard to understand how to use these things. To get you started, here's one complete test of substituteStatement that meaningfully tests the actual substitution.

@Test
public void testSubstituteStatementWithTemplatedInitializer() {
    // contract: Given a statement with a templated initializer, substituteStatement should
    // return a new statement with the initializer replaced with the value bound to the template
    // parameter

    // arrange
    Factory factory = createFactoryWithTemplates();
    CtClass<?> targetClass = factory.Class().create("TargetClass");

    String templateExecutableName = "executable";
    int templateVariableIndex = 0;
    String templateVariableName = "s";
    String initializerToSubstitute = "My chosen initializer";
    CtStatement expectedStatement = factory.createLocalVariable(
            factory.Type().stringType(), templateVariableName, factory.createLiteral(initializerToSubstitute)
    );

    StatementWithTemplatedInitializer template = new StatementWithTemplatedInitializer();
    template._initializer_ = factory.createLiteral(initializerToSubstitute);

    // act
    CtStatement substitutedStatement = Substitution.substituteStatement(targetClass, template, templateVariableIndex, templateExecutableName);

    // assert
    assertEquals(expectedStatement, substitutedStatement);
}

private static class StatementWithTemplatedInitializer extends ExtensionTemplate {
    TemplateParameter<String> _initializer_;

    public void executable() {
        String s = _initializer_.S();
    }
}

To be clear, I would like you to rewrite these tests to actually test some form of substitution.

[Rohitesh-Kumar-Jain]

I would urge you to carefully study the templating documentation to get a better idea of what the purpose of these methods is.

Thanks for sharing this, I will go through this.

here's one complete test of substituteStatement that meaningfully tests the actual substitution.

I am glad that you showed me how to correctly test this. I will rewrite tests after going through the resources that you shared

[Rohitesh-Kumar-Jain]

Should I refactor the wrongly extracted test (that I extracted in #4016) in this PR only ?

[slarse]

Now the tests are much better! Some minor comments on this revision, see code.

[Rohitesh-Kumar-Jain]

As all the suggestions are resolved for tests, should I refactor the wrongly extracted test (that I extracted in #4016)

[slarse]

Nice, LGTM!

As all the suggestions are resolved for tests, should I refactor the wrongly extracted test (that I extracted in #4016)

Let's keep this PR clean and to the point, and move that test in a separate PR.