1 files changed, 50 insertions, 0 deletions
diff --git a/internal/kwcache/fuzz_test.go b/internal/kwcache/fuzz_test.go
new file mode 100644
index 0000000..0b0eced
--- /dev/null
+++ b/internal/kwcache/fuzz_test.go
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package kwcache
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// FuzzLoad: a cache file of any content loads as a usable cache - never
+// nil, never a panic - and one that reports an error answers nothing. Its
+// answers can then be saved again.
+func FuzzLoad(f *testing.F) {
+	seed := New("fp")
+	seed.Store(a, map[string]bool{"k:acme": true, "k:x": false})
+	path := filepath.Join(f.TempDir(), "seed.cache")
+	if err := seed.Save(path, []ID{a}); err != nil {
+		f.Fatal(err)
+	}
+	good, err := os.ReadFile(path)
+	if err != nil {
+		f.Fatal(err)
+	}
+	f.Add(good)
+	f.Add([]byte(`{"version":1,"fingerprint":"fp","keywords":[["b","a"]],"files":[{"dev":1,"ino":10,"size":100,"mtime":1000,"keywords":0,"hits":[5]}]}`))
+	f.Add([]byte(`{"version":1,"fingerprint":"fp","keywords":[],"files":[{"dev":1,"ino":10,"size":100,"mtime":1000,"keywords":-1,"hits":[]}]}`))
+	f.Add([]byte("{}"))
+	f.Add([]byte("null"))
+	f.Fuzz(func(t *testing.T, data []byte) {
+		p := filepath.Join(t.TempDir(), "dl.cache")
+		if err := os.WriteFile(p, data, 0o600); err != nil {
+			t.Fatal(err)
+		}
+		c, err := Load(p, "fp")
+		if c == nil {
+			t.Fatal("Load returned a nil cache")
+		}
+		hits, ok := c.Lookup(a, []string{"k:acme", "k:x"})
+		if ok && len(hits) != 2 {
+			t.Fatalf("Lookup answered %d of 2 keywords", len(hits))
+		}
+		if err != nil && ok {
+			t.Fatalf("a cache that failed to load (%v) answered", err)
+		}
+		if err := c.Save(filepath.Join(t.TempDir(), "out.cache"), []ID{a, b}); err != nil {
+			t.Fatal(err)
+		}
+	})
+}