Specflow/Gherkin: How to handle bad data

Question

I am new to Specflow so here goes;

For my example below Should I test for the bad at all? If I do the table won't let you add a bad value. So the code will error because its coming in as as bad type. I guess I just need to know how others handle verifying the user can't enter bad data? (fields names are changed due to confidential info) the requirement says:

Verify that the user cannot set the rate to be negative or greater than 1. The rate range is from 0.9999 to 0.

Verify that the user cannot enter a rate with more than 4 decimal places.

Given the lc does not exist  
    | Lc      |
    | Test90  |  
    | Test00  | 

    When I add a Lc  
    | Lc      | Somekind of ID|  Rate     |
    | Test90  | 2             |  0.9999   |
    | Test00  | 4             |  0        |

    Then the lc should be defined
    | Lc      | 
    | Test90  |
    | Test00  | 

Answer 1

It's a bit strange that you are testing 2 values thoughout your test.

I would be tempted to rewrite like this:

Scenario Outline: valid lc's can be created
    Given the lc named <lc> does not exist  
    When I add a Lc named <lc> with Id <id> and rate <rate>
    Then the lc named <lc> should be defined
Examples:
        | Lc      | Id |  Rate     |
        | Test90  | 2  |  0.9999   |
        | Test00  | 4  |  0        |


Scenario Outline: Invalid lc's cannot be created
    Given the lc named <Lc> does not exist  
    When I add a Lc named <Lc> with Id <Id> and rate <Rate>
    Then the lc named <Lc> should not be defined
    And an error should have been raised saying the rate was invalid
Examples:
        | Lc      | ID |  Rate     |
        | Test90  | 2  |  1.999    |
        | Test90  | 2  |  0.99999  |
        | Test90  | 2  |  -0.9     |
        | Test00Y | 4  |  6        |
        | Test00Y | 4  |           |

The And an error should have been raised saying the rate was invalid step is obviously optional but shows that this is expected to fail due to an invalid rate.