Fix flaky Test flake TestReusableGoroutinesPool test

Fixes #593
Count goroutines from the current test rather than for the whole process

concurrency/worker_test.go

@@ -1,48 +1,63 @@
 package concurrency
 
 import (
+	"regexp"
 	"runtime"
+	"strings"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/require"
 )
 
 func TestReusableGoroutinesPool(t *testing.T) {
-	baseGoroutines := runtime.NumGoroutine()
-	const workers = 2
+	buf := make([]byte, 1<<20)
+	buf = buf[:runtime.Stack(buf, false)]
+	testGoroutine := regexp.MustCompile(`goroutine (\d+) \[running\]:`).FindSubmatch(buf)[1]
+	require.NotEmpty(t, testGoroutine, "test goroutine not found")
+
+	countGoroutines := func() int {
+		buf := make([]byte, 1<<20)
+		buf = buf[:runtime.Stack(buf, true)]
+		// Count the number of goroutines created by this test
+		// This ensures that the test isn't affected by leaked goroutines from other tests.
+		return strings.Count(string(buf), " in goroutine "+string(testGoroutine))
+	}
 
+	baseGoroutines := countGoroutines()
+	const workers = 2
 	w := NewReusableGoroutinesPool(workers)
-	require.Equal(t, baseGoroutines+workers, runtime.NumGoroutine())
+
+	require.Equal(t, baseGoroutines+workers, countGoroutines())
 
 	// Wait a little bit so both goroutines would be waiting on the jobs chan.
 	time.Sleep(10 * time.Millisecond)
 
 	ch := make(chan struct{})
 	w.Go(func() { <-ch })
-	require.Equal(t, baseGoroutines+workers, runtime.NumGoroutine())
+	require.Equal(t, baseGoroutines+workers, countGoroutines())
 	w.Go(func() { <-ch })
-	require.Equal(t, baseGoroutines+workers, runtime.NumGoroutine())
+	require.Equal(t, baseGoroutines+workers, countGoroutines())
 	w.Go(func() { <-ch })
-	require.Equal(t, baseGoroutines+workers+1, runtime.NumGoroutine())
+	require.Equal(t, baseGoroutines+workers+1, countGoroutines())
 
 	// end workloads, we should have only the workers again.
 	close(ch)
 	for i := 0; i < 1000; i++ {
-		if runtime.NumGoroutine() == baseGoroutines+workers {
+		if countGoroutines() == baseGoroutines+workers {
 			break
 		}
 		time.Sleep(time.Millisecond)
 	}
-	require.Equal(t, baseGoroutines+workers, runtime.NumGoroutine())
+	require.Equal(t, baseGoroutines+workers, countGoroutines())
 
 	// close the workers, eventually they should be gone.
 	w.Close()
 	for i := 0; i < 1000; i++ {
-		if runtime.NumGoroutine() == baseGoroutines {
+		if countGoroutines() == baseGoroutines {
 			return
 		}
 		time.Sleep(time.Millisecond)
 	}
-	t.Fatalf("expected %d goroutines after closing, got %d", baseGoroutines, runtime.NumGoroutine())
+	t.Fatalf("expected %d goroutines after closing, got %d", baseGoroutines, countGoroutines())
 }