private List<ValidationEvent> validateTestTraitBuiltIns(ServiceShape serviceShape, EndpointTestsTrait testSuite) {
        List<ValidationEvent> events = new ArrayList<>();
        int testIndex = 0;
        for (EndpointTestCase testCase : testSuite.getTestCases()) {
            int inputIndex = 0;
            for (EndpointTestOperationInput operationInput : testCase.getOperationInputs()) {
                for (StringNode builtInNode : operationInput.getBuiltInParams().getMembers().keySet()) {
                    validateBuiltIn(serviceShape,
                            builtInNode.getValue(),
                            operationInput,
                            "TestCase",
                            String.valueOf(testIndex),
                            "Inputs",
                            String.valueOf(inputIndex))
                            .ifPresent(events::add);
                }
                inputIndex++;
            }
            testIndex++;
        }
        return events;
    }
Validates that the built-in's specified on parameters are supported.
smithy-rules-engine/src/main/java/software/amazon/smithy/rulesengine/validators/RuleSetBuiltInValidator.java