1 files changed, 54 insertions, 0 deletions
diff --git a/src/runtime/panicnil_test.go b/src/runtime/panicnil_test.go
new file mode 100644
index 0000000..7ed98e9
--- /dev/null
+++ b/src/runtime/panicnil_test.go
@@ -0,0 +1,54 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime_test
+
+import (
+	"reflect"
+	"runtime"
+	"runtime/metrics"
+	"testing"
+)
+
+func TestPanicNil(t *testing.T) {
+	t.Run("default", func(t *testing.T) {
+		checkPanicNil(t, new(runtime.PanicNilError))
+	})
+	t.Run("GODEBUG=panicnil=0", func(t *testing.T) {
+		t.Setenv("GODEBUG", "panicnil=0")
+		checkPanicNil(t, new(runtime.PanicNilError))
+	})
+	t.Run("GODEBUG=panicnil=1", func(t *testing.T) {
+		t.Setenv("GODEBUG", "panicnil=1")
+		checkPanicNil(t, nil)
+	})
+}
+
+func checkPanicNil(t *testing.T, want any) {
+	name := "/godebug/non-default-behavior/panicnil:events"
+	s := []metrics.Sample{{Name: name}}
+	metrics.Read(s)
+	v1 := s[0].Value.Uint64()
+
+	defer func() {
+		e := recover()
+		if reflect.TypeOf(e) != reflect.TypeOf(want) {
+			println(e, want)
+			t.Errorf("recover() = %v, want %v", e, want)
+			panic(e)
+		}
+		metrics.Read(s)
+		v2 := s[0].Value.Uint64()
+		if want == nil {
+			if v2 != v1+1 {
+				t.Errorf("recover() with panicnil=1 did not increment metric %s", name)
+			}
+		} else {
+			if v2 != v1 {
+				t.Errorf("recover() with panicnil=0 incremented metric %s: %d -> %d", name, v1, v2)
+			}
+		}
+	}()
+	panic(nil)
+}