add shuffle test and news

Author: CarloLucibello

NEWS.md

@@ -7,6 +7,8 @@ been removed in favour of MLDatasets.jl.
 * `flatten` is not exported anymore due to clash with Iterators.flatten.
 * Remove Juno.jl progress bar support as it is now obsolete.
 * `Dropout` gained improved compatibility with Int and Complex arrays and is now twice-differentiable.
+* Many utily functions and the `DataLoader` are [now provided by MLUtils.jl](https://github.com/FluxML/Flux.jl/pull/1874).
+* The DataLoader is now compatible with generic dataset types implementing `MLUtils.numobs` and `MLUtils.getobs`.
 
 ## v0.12.10
 * `Dropout`/`AlphaDropout` now supports [user-specified RNGs](https://github.com/FluxML/Flux.jl/pull/1838)

test/data.jl

@@ -65,6 +65,12 @@ using Random
     @test batches[3][1] == batches[3].x == X[:,5:5]
     @test batches[3][2] == batches[3].y == Y[5:5]
 
+    # Don't mutate state https://github.com/FluxML/Flux.jl/issues/1227
+    d = DataLoader([1:10;], shuffle=true)
+    cd = collect(zip(d, d))
+    # skip the first since it used to be different also before fixing the bug
+    @test [cd[i][1] for i=2:10] != [cd[i][2] for i=2:10] 
+    
     # test interaction with `train!`
     θ = ones(2)
     X = zeros(2, 10)