added test

Author: pvprajwal

test/array.jl

@@ -61,6 +61,8 @@ end
     @test_throws "Metal does not support Int128 values" MtlArray(Int128[1])
     @test_throws "Metal does not support UInt128 values" MtlArray(UInt128[1])
 
+    @test_throws "Invalid MTL storage mode" MtlArray{Int,1,2}(undef, 2)
+
     @test collect(Metal.zeros(2, 2)) == zeros(Float32, 2, 2)
     @test collect(Metal.ones(2, 2)) == ones(Float32, 2, 2)