1 files changed, 66 insertions, 0 deletions
diff --git a/src/cmd/go/testdata/script/test_fuzz_mutator_repeat.txt b/src/cmd/go/testdata/script/test_fuzz_mutator_repeat.txt
new file mode 100644
index 0000000000..0924ed37e6
--- /dev/null
+++ b/src/cmd/go/testdata/script/test_fuzz_mutator_repeat.txt
@@ -0,0 +1,66 @@
+# TODO(jayconrod): support shared memory on more platforms.
+[!darwin] [!linux] [!windows] skip
+
+# Verify that the fuzzing engine records the actual crashing input, even when
+# a worker process terminates without communicating the crashing input back
+# to the coordinator.
+
+[short] skip
+
+# Start fuzzing. The worker crashes after ~100 iterations.
+# The fuzz function writes the crashing input to "want" before exiting.
+# The fuzzing engine reconstructs the crashing input and saves it to testdata.
+! exists want
+! go test -fuzz=. -parallel=1
+stdout 'fuzzing process terminated unexpectedly'
+stdout 'Crash written to testdata'
+
+# Run the fuzz target without fuzzing. The fuzz function is called with the
+# crashing input in testdata. The test passes if that input is identical to
+# the one saved in "want".
+exists want
+go test -want=want
+
+-- go.mod --
+module fuzz
+
+go 1.17
+-- fuzz_test.go --
+package fuzz
+
+import (
+	"bytes"
+	"flag"
+	"os"
+	"testing"
+)
+
+var wantFlag = flag.String("want", "", "file containing previous crashing input")
+
+func FuzzRepeat(f *testing.F) {
+	i := 0
+	f.Fuzz(func(t *testing.T, b []byte) {
+		i++
+		if i == 100 {
+			f, err := os.OpenFile("want", os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0666)
+			if err != nil {
+				// Couldn't create the file, probably because it already exists,
+				// and we're minimizing now. Return without crashing.
+				return
+			}
+			f.Write(b)
+			f.Close()
+			os.Exit(1) // crash without communicating
+		}
+
+		if *wantFlag != "" {
+			want, err := os.ReadFile(*wantFlag)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !bytes.Equal(want, b) {
+				t.Fatalf("inputs are not equal!\n got: %q\nwant:%q", b, want)
+			}
+		}
+	})
+}