all: add test on linux

Author: changkun

.github/workflows/mainthread.yml

@@ -2,12 +2,11 @@ name: mainthread
 
 on:
   push:
-    branches: [ master ]
+    branches: [ main ]
   pull_request:
-    branches: [ master ]
+    branches: [ main ]
 
 jobs:
-
   build:
     name: Build
     runs-on: ubuntu-latest
@@ -28,8 +27,3 @@ jobs:
     - name: Test
       run: |
         go test -v -coverprofile=coverage.txt -covermode=atomic ./...
-    - name: Upload coverage profile
-      uses: codecov/codecov-action@v1
-      with:
-        token: ${{secrets.CODECOV_TOKEN}}
-        file: coverage.txt

README.md

@@ -1,7 +1,7 @@
 # mainthread
 
 [![PkgGoDev](https://pkg.go.dev/badge/golang.design/x/mainthread)](https://pkg.go.dev/golang.design/x/mainthread) [![Go Report Card](https://goreportcard.com/badge/golang.design/x/mainthread)](https://goreportcard.com/report/golang.design/x/mainthread)
-![mainthread](https://github.com/golang-design/mainthread/workflows/mainthread/badge.svg?branch=master)
+![mainthread](https://github.com/golang-design/mainthread/workflows/mainthread/badge.svg?branch=main)
 
 Package mainthread schedules function calls on the main thread in Go.
 

go.mod

@@ -1,3 +1,5 @@
 module golang.design/x/mainthread
 
 go 1.15
+
+require golang.org/x/sys v0.0.0-20201022201747-fb209a7c41cd

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/sys v0.0.0-20201022201747-fb209a7c41cd h1:WgqgiQvkiZWz7XLhphjt2GI2GcGCTIZs9jqXMWmH+oc=
+golang.org/x/sys v0.0.0-20201022201747-fb209a7c41cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

mainthread_test.go

@@ -6,19 +6,60 @@ package mainthread_test
 
 import (
 	"fmt"
+	"os"
+	"sync"
+	"sync/atomic"
 	"testing"
 
 	"golang.design/x/mainthread"
+	"golang.org/x/sys/unix"
 )
 
-func TestMainthread(t *testing.T) {
+var initTid int
+
+func init() {
+	initTid = unix.Getpid()
+}
+
+func TestMain(m *testing.M) {
 	mainthread.Init(func() {
-		mainthread.Call(func() {
-			// FIXME: how to test this function really runs on the main thread?
-		})
+		os.Exit(m.Run())
 	})
 }
 
+func TestMainThread(t *testing.T) {
+	var (
+		nummain uint64
+		numcall = 100000
+	)
+
+	wg := sync.WaitGroup{}
+	for i := 0; i < numcall; i++ {
+		wg.Add(2)
+		go func() {
+			defer wg.Done()
+			mainthread.Call(func() {
+				tid := unix.Gettid()
+				if tid == initTid {
+					return
+				}
+				t.Fatalf("call is not executed on the main thread, want %d, got %d", initTid, tid)
+			})
+		}()
+		go func() {
+			defer wg.Done()
+			if unix.Gettid() == initTid {
+				atomic.AddUint64(&nummain, 1)
+			}
+		}()
+	}
+	wg.Wait()
+
+	if nummain == uint64(numcall) {
+		t.Fatalf("all non main thread calls are executed on the main thread.")
+	}
+}
+
 func BenchmarkCall(b *testing.B) {
 	f1 := func() {}
 	f2 := func() {}