test: reproduce a race condition

1 files changed, 62 insertions, 0 deletions

diff --git a/app/db/in_memory_repository_test.go b/app/db/in_memory_repository_test.go
index cf516aa..37fcbe0 100644
--- a/app/db/in_memory_repository_test.go
+++ b/app/db/in_memory_repository_test.go
@@ -1,6 +1,8 @@
 package db
 
 import (
+	"context"
+	"sync"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -29,6 +31,66 @@ func TestInMemoryRepository(t *testing.T) {
 			assert.Equal(t, "@tanuki", sparkles[0].Sparklee)
 			assert.Equal(t, "because", sparkles[0].Reason)
 		})
+
+		t.Run("prevents race conditions", func(t *testing.T) {
+			repository := NewRepository[*domain.Sparkle]()
+			ctx := context.Background()
+
+			numGoroutines := 100
+			numOperationsPerGoroutine := 50
+
+			var wg sync.WaitGroup
+			errors := make(chan error, numGoroutines*2)
+
+			for i := 0; i < numGoroutines; i++ {
+				wg.Add(1)
+				go func(workerID int) {
+					defer wg.Done()
+					defer func() {
+						if r := recover(); r != nil {
+							errors <- assert.AnError
+						}
+					}()
+
+					for j := 0; j < numOperationsPerGoroutine; j++ {
+						if err := repository.Save(ctx, &domain.Sparkle{
+							Sparklee: "@user" + string(rune(workerID)),
+							Reason:   "for running concurrently",
+						}); err != nil {
+							errors <- err
+							return
+						}
+					}
+				}(i)
+			}
+
+			for i := 0; i < numGoroutines; i++ {
+				wg.Add(1)
+				go func() {
+					defer wg.Done()
+					defer func() {
+						if r := recover(); r != nil {
+							errors <- assert.AnError
+						}
+					}()
+
+					for j := 0; j < numOperationsPerGoroutine; j++ {
+						_ = repository.All(ctx)
+					}
+				}()
+			}
+
+			wg.Wait()
+			close(errors)
+
+			var raceErrors []error
+			for err := range errors {
+				raceErrors = append(raceErrors, err)
+			}
+
+			assert.Equal(t, numGoroutines*numOperationsPerGoroutine, len(repository.All(ctx)))
+			assert.Empty(t, raceErrors)
+		})
 	})
 
 	t.Run("Find", func(t *testing.T) {