add simple unit test

backend/controller/dal/async_calls_test.go

@@ -0,0 +1,22 @@
+package dal
+
+import (
+	"context"
+	"testing"
+
+	"github.com/TBD54566975/ftl/backend/controller/sql/sqltest"
+	dalerrs "github.com/TBD54566975/ftl/backend/dal"
+	"github.com/TBD54566975/ftl/internal/log"
+	"github.com/alecthomas/assert/v2"
+)
+
+func TestNoCallToAcquire(t *testing.T) {
+	ctx := log.ContextWithNewDefaultLogger(context.Background())
+	conn := sqltest.OpenForTesting(ctx, t)
+	dal, err := New(ctx, conn)
+	assert.NoError(t, err)
+
+	_, err = dal.AcquireAsyncCall(ctx)
+	assert.IsError(t, err, dalerrs.ErrNotFound)
+	assert.EqualError(t, err, "no pending async calls: not found")
+}