Fix #123: Deduplicate result errors

core/result_test.go

@@ -0,0 +1,21 @@
+package core
+
+import (
+	"testing"
+)
+
+func TestResult_AddError(t *testing.T) {
+	result := &Result{}
+	result.AddError("potato")
+	if len(result.Errors) != 1 {
+		t.Error("should've had 1 error")
+	}
+	result.AddError("potato")
+	if len(result.Errors) != 1 {
+		t.Error("should've still had 1 error, because a duplicate error was added")
+	}
+	result.AddError("tomato")
+	if len(result.Errors) != 2 {
+		t.Error("should've had 2 error")
+	}
+}