Arcade Error:Test execution error: Cannot read properties of undefined (reading 'toString'). Verify test data.

SaraWazir — Tue, 10 Mar 2026 04:42:27 GMT

Hi,

I have an arcade expression where I am pulling an attribute from a related record. I have normally used something like this for other data and pop ups and it has worked fine. For this current data I am working with, I got this error and I cannot figure out what this error means and what I can do to solve my problem and display my related record:

Expression:

var relFS = FeatureSetByRelationshipName($feature, "Project_Locations", ['Proj_Desc'], true)

var relFeature = First(relFS);

if (!IsEmpty(relFeature)) {

return relFeature.Proj_Desc;

} else {

return "No project description available";

}

Error:

Test execution error: Cannot read properties of undefined (reading 'toString'). Verify test data.

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Arcade Error:Test execution error: Cannot read properties of undefined (reading 'toString'). Verify test data.