Customise FsCheck output

I am testing with FsCheck and NUnit in VisualStudio.

The problem currently is: I managed to generate random graphs (for testing some graph functionality) but when a test fails, FsCheck spits out the whole graph and it does not use ToString so it literally dumps raw list of records and you cannot see anything in there.

Also I would need not only the input graph for inspection but also some other data that I create when running a property.

So how can I change the output behaviour of FsCheck in order to

• actually call my ToString method on the input graph
• output further information

when a test fails?

EDIT: Here is my current test setup.

module GraphProperties

open NUnit.Framework
open FsCheck
open FsCheck.NUnit

let generateRandomGraph =
    gen {
        let graph: Graph<int,int> = Graph<_,_>.Empty()
        // fill in random nodes and transitions...
        return graph
    }

type MyGenerators =
    static member Graph() =
        {new Arbitrary<Graph<int,int>>() with
            override this.Generator = generateRandomGraph
            override this.Shrinker _ = Seq.empty }

[<TestFixture>]
type NUnitTest() =
    [<Property(Arbitrary=[|typeof<MyGenerators>|], QuietOnSuccess = true)>]
    member __.cloningDoesNotChangeTheGraph (originalGraph: Graph<int,int>) =
        let newGraph = clone originalGraph
        newGraph = originalGraph