Stuck writing a test class for ContentDocumentLink object apex trigger

Question

I am trying to write a test class so that I can send the following trigger live in our production system:

trigger updateDocTitleFileExt on ContentDocumentLink (after insert) {
    for (ContentDocumentLink li : Trigger.new) {
        Map<String, Object> params = new Map<String, Object>();
        params.put('content_doc_link_id', li.Id);
        Flow.Interview.GIS_Design_Update_File_Title updDocTitleFileExt = new Flow.Interview.GIS_Design_Update_File_Title(params);
        updDocTitleFileExt.start();
    }    
}

Heres the code for the Apex Test Class that I've written:

@isTest
public class TestUpdateDocTitleFileExt {
    @isTest static void TestUpdateDocTitleFileExt() {

        // Create a case
        Case cse = new Case(Subject='Test Case For Apex Trigger');
        insert cse;

        ContentVersion contentVersionInsert = new ContentVersion(
                            Title = 'Test',
                            PathOnClient = 'Test.jpg',
                            VersionData = Blob.valueOf('Test Content Data'),
                            IsMajorVersion = true);
        insert contentVersionInsert;

        // Test INSERT
        ContentVersion contentVersionSelect = [SELECT Id, Title, ContentDocumentId FROM ContentVersion WHERE Id = :contentVersionInsert.Id LIMIT 1];
        List<ContentDocument> documents = [SELECT Id, Title, LatestPublishedVersionId FROM ContentDocument];
        System.assertEquals(documents.size(), 1);

        // Perform test
        Test.startTest();
        Test.stopTest();
    }
}

This all saves fine - but I'm getting the below error

"INVALID_ARGUMENT_TYPE" error, "argument is null or invalid", "Class.textUpdateCocTitleFileExt line 10, column 1"

when I try and run it as a test.

I've had a really good google of this error and have tried a load of code changes out but whatever I try I just can't ever seem to get round this particular error on line 10.

Anyone got any thoughts to help me get a pass on it?

Answer 1

not sure why this works and yours doesn't, but this works for me:

String clientPath = 'photo_1.jpg';
ContentVersion cv = new ContentVersion(
    title='test',
    versiondata=Blob.valueOf('test'),
    pathonclient=clientPath
);