Cover autogenerated end-range validators by unit tests in processor

[aababilov]

Cover autogenerated end-range validators by unit tests in processor

Annotation processor generates validators based on @EndRange annotation. There should be unit tests that cover the following behavior:

• the generated code looks literally as expected when @EndRange annotation is applied;
• allowEqual option works as expected with false and true values;
• error messages are generated when EndRange.field does not reference an existing field;
• error messages are generated when EndRange.field references the start field.