test mul! for out-of-place FunctionOperator

Author: cvsvensson

test/func.jl

@@ -167,7 +167,7 @@ end
 
     # Test standard operator operations (from original test)
     w = rand(N, K)
-    @test _mul(A, v) ≈ op1 * v ≈ mul!(w, op2, v)
+    @test _mul(A, v) ≈ op1 * v ≈ mul!(w, op2, v) ≈ mul!(w, op1, v) 
     w = rand(N, K)
     @test _mul(A, v) ≈ op1(v, u, p, t) ≈ op2(v, u, p, t)
     v = rand(N, K)