sync: add tests

src/sync/waitgroup_test.go

@@ -0,0 +1,35 @@
+package sync_test
+
+import (
+	"sync"
+	"testing"
+)
+
+// TestWaitGroupUncontended tests the wait group from a single goroutine.
+func TestWaitGroupUncontended(t *testing.T) {
+	// Check that a single add-and-done works.
+	var wg sync.WaitGroup
+	wg.Add(1)
+	wg.Done()
+	wg.Wait()
+
+	// Check that mixing positive and negative counts works.
+	wg.Add(10)
+	wg.Add(-8)
+	wg.Add(-1)
+	wg.Add(0)
+	wg.Done()
+	wg.Wait()
+}
+
+// TestWaitGroup tests the typical usage of WaitGroup.
+func TestWaitGroup(t *testing.T) {
+	const n = 5
+	var wg sync.WaitGroup
+	wg.Add(n)
+	for i := 0; i < n; i++ {
+		go wg.Done()
+	}
+
+	wg.Wait()
+}