Add test cases for IsZeroOfUnderlyingType

Signed-off-by: aeneasr <3372410+aeneasr@users.noreply.github.com>

associations/association.go

@@ -160,5 +160,9 @@ func fieldIsNil(f reflect.Value) bool {
 
 // IsZeroOfUnderlyingType will check if the value of anything is the equal to the Zero value of that type.
 func IsZeroOfUnderlyingType(x interface{}) bool {
+	if x == nil {
+		return true
+	}
+
 	return reflect.DeepEqual(x, reflect.Zero(reflect.TypeOf(x)).Interface())
 }

associations/association_test.go

@@ -0,0 +1,37 @@
+package associations
+
+import (
+	"database/sql"
+	"fmt"
+	"github.com/gobuffalo/nulls"
+	"github.com/gofrs/uuid"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func Test_IsZeroOfUnderlyingType(t *testing.T) {
+	for k, tc := range []struct {
+		in   interface{}
+		zero bool
+	}{
+		{in: nil, zero: true},
+		{in: 0, zero: true},
+		{in: 1, zero: false},
+		{in: false, zero: true},
+		{in: "", zero: true},
+		{in: interface{}(nil), zero: true},
+		{in: uuid.NullUUID{}, zero: true},
+		{in: uuid.UUID{}, zero: true},
+		{in: uuid.NullUUID{Valid: true}, zero: false},
+		{in: nulls.Int{}, zero: true},
+		{in: nulls.String{}, zero: true},
+		{in: nulls.Bool{}, zero: true},
+		{in: nulls.Float64{}, zero: true},
+		{in: sql.NullString{}, zero: true},
+		{in: sql.NullString{Valid: true}, zero: false},
+	} {
+		t.Run(fmt.Sprintf("case=%d", k), func(t *testing.T) {
+			assert.EqualValues(t, tc.zero, IsZeroOfUnderlyingType(tc.in))
+		})
+	}
+}