How to verify all collections are instanced in all entities in the context

I have a DbContext with multiple DbSet<> properties. Some of those DbSet<> have Icollection<> objects (navigation properties).

I want to write a unit test which checks if all those ICollection<> properties are instanced in my entities constructors.

Here is where I am this far:

// this.ctx is the instance of my DbContext
var allProps = this.ctx.GetType().GetProperties();
var allDbSets = allProps.Where(pi => pi.PropertyType.IsGenericType && pi.PropertyType.GetGenericTypeDefinition() == typeof(DbSet<>));
var allEntities = allDbSets.SelectMany(pi => pi.PropertyType.GetGenericArguments());

foreach (var entity in allEntities)
{
    // get collections of entity
    var genericProps = entity.GetProperties().Where(pi => pi.PropertyType.IsGenericType);
    var collections = genericProps.Where(pi => pi.PropertyType.GetGenericTypeDefinition() == typeof(ICollection<>));

    if(collections.Any())
    {
        foreach (var coll in collections)
        {
            // coll is the PropertyInfo of a ICollection<> object.
        }
    }
}

From there I'm blocked. I don't see how I can test that the collection is instanced.

Thanks for your help!