add the design.md for the calculator-conundrum

Author: xinri

exercises/concept/calculator-conundrum/.meta/design.md

@@ -18,3 +18,15 @@
 
 - `conditionals-if`: know how to do conditional logic.
 - `switch-statement`: know how to work with a `switch` statement.
+
+## Analyzer
+
+This exercise could benefit from the following rules in the [analyzer]:
+
+- `essential`: Verify that the solution is using the try catch statement for the division.
+- `actionable`: If the solution is wrapping all the code in a try catch statement, instruct the student to only use the `try catch` for the division statement
+- `actionable`: If the solution uses only `if` statement, instruct the student that he/she can use the `switch case` statement to perform the operation.
+- `informative`: If the solution does not throw the exception for `Operation cannot be null` and `Operation cannot be empty` at the beginning, suggest the fail-fast approach to the student.
+  Inform this way of implementation can be less error-prone and more readable as suggested by Martin Fowler: https://martinfowler.com/ieeeSoftware/failFast.pdf
+
+[analyzer]: https://github.com/exercism/java-analyzer