Written a testclass on feeditem, but no luck(its 0%) - not sure about the mistake in my code. Please do help me out and de needful.

Trigger :

```
trigger RestrictFilesOnFeedItems on FeedItem (after insert) {
    Map<Id, FeedItem> contentversionIdToFeedItemMap = new Map<Id, FeedItem>();
    for(FeedItem fi : trigger.new){
        if(fi.type == 'ContentPost')
            contentversionIdToFeedItemMap.put(fi.RelatedRecordId, fi);
    }
    for(ContentVersion cv : [SELECT Id, FileExtension,FileType FROM ContentVersion where Id IN :contentversionIdToFeedItemMap.keySet()]){
    if(cv.FileType =='exe' || cv.FileType=='html' || cv.FileType=='edi'|| cv.FileType=='dll'|| cv.FileType=='bin'|| cv.FileType=='cmd'|| cv.FileType=='vbscript'|| cv.FileType=='wsf'|| cv.FileType=='java'|| cv.FileType=='vbs'|| cv.FileType=='vb')
    {
        contentversionIdToFeedItemMap.get(cv.Id).addError('Sorry..!! You cannot attach this file format');
    }

```

Test Class:

```
@isTest(seeAlldata = true)
private class RestrictFilesOnFeedItems_Test {
    static testMethod void unitTestInsert() {
        id abc = 'EXE' ;
    Case cse = new case (COMPLAINANT__C = 'Self', STATUS = 'New', ORIGIN = 'Web', TYPE='Claims', SR_SUB_TYPE__C = 'Report Claim', SUBJECT = 'Test', DESCRIPTION= 'Testing');
        Insert cse;
        /*
        Profile p = [select id from profile where Name = :'System Administrator' limit 1];
        User pu = new User(profileId = p.id, username = 'abc@abc.com', email = 'abc@abc.com',
        emailencodingkey = 'UTF-8', localesidkey = 'en_US',
        languagelocalekey = 'en_US', timezonesidkey = 'America/Los_Angeles',
        alias='cspu', lastname='lastname');
        insert pu;
        */
        ContentVersion  cv = new ContentVersion ();
        insert cv;
        Test.startTest();
        FeedItem feed = new FeedItem (
            parentid = cse.id,
            type = 'ContentPost',
            RelatedRecordId = cv.id,
            Body = 'Hello'
        );
        try {
            insert feed;
        } catch (exception e) {
            System.assert(e.getMessage().contains('Sorry..!! You cannot attach this file format'));
        }
        Test.stopTest();
        List<FeedItem > lstfeed = [select id from FeedItem where parent.id = :cse.id];
        System.assertEquals(1, lstfeed.size());
        System.assertNotEquals(0, lstfeed.size());
    }
}

```