1 files changed, 44 insertions, 0 deletions
diff --git a/internal/ignore/fuzz_test.go b/internal/ignore/fuzz_test.go
new file mode 100644
index 0000000..0e9f0a3
--- /dev/null
+++ b/internal/ignore/fuzz_test.go
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package ignore
+
+import (
+	"strings"
+	"testing"
+)
+
+// FuzzMatch: any pattern either fails to compile or matches any walked
+// path without panicking, and gives the same answer twice. The oracle test
+// checks answers against git; this checks everything else.
+func FuzzMatch(f *testing.F) {
+	for _, p := range []string{"*.log", "/a.txt", "build/", "**/readme.md", "[!a]*.txt", "[[:digit:]]*", `\`, "[", "a[/]b", "!", "**/**/**", "*a*a*a*b"} {
+		f.Add(p, "dir/sub/a.txt")
+	}
+	f.Fuzz(func(t *testing.T, pattern, rel string) {
+		m, err := New([]string{pattern})
+		if err != nil {
+			return
+		}
+		rel = walkedRel(rel)
+		if rel == "" {
+			return
+		}
+		if m.Match(rel, false) != m.Match(rel, false) {
+			t.Fatalf("Match(%q) under %q is not deterministic", rel, pattern)
+		}
+		m.Match(rel, true)
+	})
+}
+
+// walkedRel turns any string into a path of the shape Match accepts, as a
+// directory walk produces it: slash-separated, with no empty, "." or ".."
+// components.
+func walkedRel(s string) string {
+	var parts []string
+	for _, p := range strings.Split(s, "/") {
+		if p != "" && p != "." && p != ".." {
+			parts = append(parts, p)
+		}
+	}
+	return strings.Join(parts, "/")
+}