chore: add test

tariff/helper.go

@@ -81,9 +81,9 @@ type runnable interface {
 func runOrError[T any, I interface {
 	*T
 	runnable
-}](t *T) (*T, error) {
+}](t I) (*T, error) {
 	done := make(chan error)
-	go I(t).run(done)
+	go t.run(done)
 
 	if err := <-done; err != nil {
 		return nil, err

tariff/helper_test.go

@@ -1,6 +1,7 @@
 package tariff
 
 import (
+	"errors"
 	"testing"
 	"time"
 
@@ -55,3 +56,28 @@ func TestMergeRatesAfter(t *testing.T) {
 		assert.Equal(t, tc.expected, res)
 	}
 }
+
+type runner struct {
+	res error
+}
+
+func (r *runner) run(done chan error) {
+	if r.res == nil {
+		close(done)
+	} else {
+		done <- r.res
+	}
+}
+
+func TestRunOrQError(t *testing.T) {
+	{
+		res, err := runOrError(&runner{nil})
+		require.NoError(t, err)
+		require.NotNil(t, res)
+	}
+	{
+		res, err := runOrError(&runner{errors.New("foo")})
+		require.Error(t, err)
+		require.Nil(t, res)
+	}
+}