@Override
        public String toString() {
            StringBuilder builder = new StringBuilder();

            builder.append("=======================\n"
                    + "Model Validation Result\n"
                    + "=======================\n")
                    .append(getModelLocation())
                    .append('\n');

            if (!getUnmatchedEvents().isEmpty()) {
                builder.append("\nDid not match the following events\n"
                        + "----------------------------------\n");
                for (ValidationEvent event : getUnmatchedEvents()) {
                    builder.append(event.toString().replace("\n", "\\n")).append('\n');
                }
                builder.append('\n');
            }

            if (!getExtraEvents().isEmpty()) {
                builder.append("\nEncountered unexpected events\n"
                        + "-----------------------------\n");
                for (ValidationEvent event : getExtraEvents()) {
                    builder.append(event.toString().replace("\n", "\\n")).append("\n");
                }
                builder.append('\n');
            }

            return builder.toString();
        }
Output of validating a model against a test case.
smithy-model/src/main/java/software/amazon/smithy/model/validation/testrunner/SmithyTestCase.java