Add panic handler test, remove redundant "graphql:" prefix

errors/panic_handler.go

@@ -14,5 +14,5 @@ type DefaultPanicHandler struct{}
 
 // MakePanicError creates a new QueryError from a panic that occurred during execution
 func (h *DefaultPanicHandler) MakePanicError(ctx context.Context, value interface{}) *QueryError {
-	return Errorf("graphql: panic occurred: %v", value)
+	return Errorf("panic occurred: %v", value)
 }

errors/panic_handler_test.go

@@ -0,0 +1,24 @@
+package errors
+
+import (
+	"context"
+	"testing"
+)
+
+func TestDefaultPanicHandler(t *testing.T) {
+	handler := &DefaultPanicHandler{}
+	qErr := handler.MakePanicError(context.Background(), "foo")
+	if qErr == nil {
+		t.Fatal("Panic error must not be nil")
+	}
+	const (
+		expectedMessage = "panic occurred: foo"
+		expectedError   = "graphql: " + expectedMessage
+	)
+	if qErr.Error() != expectedError {
+		t.Errorf("Unexpected panic error message: %q != %q", qErr.Error(), expectedError)
+	}
+	if qErr.Message != expectedMessage {
+		t.Errorf("Unexpected panic QueryError.Message: %q != %q", qErr.Message, expectedMessage)
+	}
+}