add test for max int64 validator

internal/block/int64_component/int64_component.go

@@ -58,12 +58,14 @@ func (t *Int64ComponentInstance) Value() interface{} {
 
 func (t *Int64ComponentInstance) FromJSON(component block.Component, data json.RawMessage) error {
 	var s int64
-	err := json.Unmarshal(data, &s)
-	if err != nil {
-		return fmt.Errorf("Error unmarshalling property %s: %w", component.Identifier(), err)
-	}
 
-	t.value = s
+	if data != nil {
+		err := json.Unmarshal(data, &s)
+		if err != nil {
+			return err
+		}
+		t.value = s
+	}
 
 	for _, v := range component.Validators() {
 		if err := v(s); err != nil {

internal/block/int64_component/validators/max_test.go

@@ -0,0 +1,37 @@
+package int64_component_validators
+
+import (
+	"blocky/internal/block/int64_component"
+	"testing"
+)
+
+func TestMax(t *testing.T) {
+	cfg := &int64_component.Int64ComponentConfig{}
+	Max(10)(cfg)
+
+	if len(cfg.Validators) != 1 {
+		t.Fatalf("expect 1 validator, got %d", len(cfg.Validators))
+	}
+
+	validate := cfg.Validators[0]
+
+	tests := []struct {
+		name    string
+		value   int64
+		wantErr bool
+	}{
+
+		{"below value", 5, false},
+		{"equal to value", 10, false},
+		{"above value", 15, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := validate(tt.value)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("validate(%v) error = %v, wanterr %v", tt.value, err, tt.wantErr)
+			}
+		})
+	}
+}