test: add multi-threads jpeg_encode test

Author: johnnychen94

.github/workflows/UnitTest.yml

@@ -45,4 +45,20 @@ jobs:
       - uses: codecov/codecov-action@v2
         with:
           files: lcov.info
-
+  multithreads:
+    name: Julia (threads) 1 - ubuntu-latest - x64 - ${{ github.event_name }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: julia-actions/setup-julia@v1
+        with:
+          version: '1'
+          arch: 'x64'
+      - uses: julia-actions/cache@v1
+      - uses: julia-actions/julia-buildpkg@v1
+      - name: run test
+        run: julia --project --code-coverage -t4 -e 'using Pkg; Pkg.test()'
+      - uses: julia-actions/julia-processcoverage@v1
+      - uses: codecov/codecov-action@v2
+        with:
+          files: lcov.info

test/runtests.jl

@@ -47,4 +47,10 @@ end
     end
 
     include("tst_encode.jl")
+    if Threads.nthreads() > 1
+        @info "Multi-threads test: enabled"
+        include("tst_multithreads.jl")
+    else
+        @info "Multi-threads test: skipped"
+    end
 end

test/tst_multithreads.jl

@@ -0,0 +1,14 @@
+@testset "multithreads" begin
+    @test Threads.nthreads() > 1
+
+    img = testimage("lighthouse")
+    @testset "jpeg_encode" begin
+        ref = jpeg_encode(img)
+
+        out = [fill(zero(UInt8), size(ref)) for _ in 1:Threads.nthreads()]
+        Threads.@threads for i in 1:Threads.nthreads()
+            out[i] = jpeg_encode(img)
+        end
+        @test all(out .== Ref(ref))
+    end
+end