code: public ValidationAssert isValid() {
          ValidationResult validationResult = validate();
          if (!validationResult.isValid()) {
              throwAssertionError(shouldBeValid(actual.getSystemId(), validationResult.getProblems()));
          }
          return this;
      }
docs: Verifies that actual value is valid against given schema
  
  @throws AssertionError if the actual value is not valid against schema