add multithreaded save test

.appveyor.yml

@@ -1,4 +1,5 @@
 environment:
+  JULIA_NUM_THREADS: 2
   matrix:
   - julia_version: 0.7
   - julia_version: 1.0

.travis.yml

@@ -7,6 +7,8 @@ julia:
   - 1.0
   - 1
   - nightly
+env:
+  - JULIA_NUM_THREADS=2
 matrix:
   allow_failures:
     - julia: nightly

test/loadsave.jl

@@ -255,6 +255,13 @@ end # module Dummy
     @test load(fn) == a
     rm(fn)
 
+    if Threads.nthreads() > 1
+        Threads.@threads for i in 1:(Threads.nthreads() * 5)
+            fn = string(tempname(), ".dmy")
+            save(fn, a)
+        end
+    end
+
     # force format
     fn = string(tempname(), ".dmy")
     savestreaming(format"DUMMY", fn) do writer

test/runtests.jl

@@ -2,6 +2,8 @@ using FileIO
 using FilePathsBase
 using Test
 
+Threads.nthreads() <= 1 && @info "Threads.nthreads() = $(Threads.nthreads()), multithread tests will be disabled"
+
 # Both FileIO and FilePathsBase export filename, but we only want the FileIO definition.
 using FileIO: filename