Get all entries with linked entry in entries field
Have you read the docs about relations? 

'criteria' =&gt; [
    'section' =&gt; 'projects', 
    'test' =&gt; 'testValue' 
    'relatedTo' =&gt; id
]


Just replace id with the ID of your element 

If you want to filter a specific field you have to include it as an array 

'relatedTo' =&gt; [
    'sourceElement' =&gt; id,
    'field' =&gt; 'fieldHandle'
]