@Override
    public List<ValidationEvent> validate(Model model) {
        List<ValidationEvent> events = new ArrayList<>();
        Stream.concat(model.shapes(OperationShape.class), model.shapes(StructureShape.class)).forEach(shape -> {
            shape.getTrait(HttpMalformedRequestTestsTrait.class).ifPresent(trait -> {
                trait.getParameterizedTestCases().forEach(testCase -> {
                    if (!testCase.getTestParameters().isEmpty()) {
                        Set<Integer> sizes = testCase.getTestParameters()
                                .values()
                                .stream()
                                .map(List::size)
                                .collect(Collectors.toSet());
                        if (sizes.size() != 1) {
                            events.add(error(shape,
                                    trait.getSourceLocation(),
                                    "Each list associated to a key "
                                            + "in `testParameters` must be of the same length."));
                        }
                    }
                });
            });
        });
        return events;
    }
Ensures that parameters attached to @httpMalformedRequestTest cases are well-formed.
smithy-protocol-test-traits/src/main/java/software/amazon/smithy/protocoltests/traits/HttpMalformedRequestTestsValidator.java