How to feed a list of lists as an argument into a Robot Framework Test Template

Question

I have the template keyword for my "do any combination" test, where ${labels} is a list and ${versions} is a list of lists:

TT Process Instance Version Search
    [Arguments]     ${labels}    ${versions}
    Login
    Process Instance Version Search     ${labels}    ${versions}

Then I create a test-suite file and place the following:

*** Settings ***
Test Template   TT Process Instance Version Search


*** Variables ***
@{ProcessVersions} =   ${Process0}     ${Process1}     ${Process2}
@{SingleVersion} =  ${Process2}
@{Process0} =   1   2
@{Process1} =   3   test_version
@{Process2} =   1

@{SingleProcessLabel} =  Label1
@{ProcessLabels} =  Label1     Label2   Label3

    *** Test Cases ***                                     
Single Instance Version for a Single Process     ${SingleProcessLabel}   ${SingleVersion}
Distinct Instance Versions for Multiple Processes    ${ProcessLabels}  ${ProcessVersions}

The error message I get is "List variable '@{versions}' has no item in index 0."

I played a lot with this, including using embedded arguments, and the only way I managed fixing it, is providing $versions directly as a global variable. My code works fine with global variables, but I have to change data manually. What I really need is implement data-driven design.

Thanks a lot for any suggestions and help!

Answer 1

From a comment to the question you wrote:

The question is: How to feed list of lists as an argument into a Test template?

The answer to that is documented in the robot framework user guide, in the section titled List Variables. When calling a keyword, if you use a $ in front of the variable, the variable will be treated as a list object. If you use @, the variable will be split into multiple arguments.

When writing a keyword that accepts arguments, the same is true. If you want a single argument, use a $ for the argument variable. If you want to collect all arguments as a list, use @.

Here is a test that shows a couple of examples:

*** Variables ***
@{numbers}    1    2    3
@{letters}    a    b    c    d
@{listoflists}    ${numbers}    ${letters}

*** Keywords ***
Accept list of lists as single arg
    [Arguments]         ${arguments}
    length should be    ${arguments}       2
    length should be    ${arguments[0]}    3
    length should be    ${arguments[1]}    4

Accept multiple args
    [Arguments]         @{arguments}
    length should be    ${arguments}       2
    length should be    ${arguments[0]}    3
    length should be    ${arguments[1]}    4


*** Test cases ***
Pass list of lists as single argument
    Accept list of lists as single arg       ${listoflists}

Pass list of lists as multiple arguments
    Accept multiple args    @{listoflists}
    Accept multiple args    ${numbers}    ${letters}