multi: add fuzzer to make

.github/workflows/main.yml

@@ -106,6 +106,7 @@ jobs:
         unit_type:
           - unit-race
           - unit-cover
+          - fuzz
     steps:
       - name: git checkout
         uses: actions/checkout@v2

Makefile

@@ -12,6 +12,7 @@ GOIMPORTS_BIN := $(GO_BIN)/gosimports
 GOBUILD := go build -v
 GOINSTALL := go install -v
 GOTEST := go test -v
+GOFUZZ := go test -fuzztime 1m -fuzz
 
 GOFILES_NOVENDOR = $(shell find . -type f -name '*.go' -not -path "./vendor/*" -not -name "*pb.go" -not -name "*pb.gw.go" -not -name "*.pb.json.go")
 GOLIST := go list -deps $(PKG)/... | grep '$(PKG)'| grep -v '/vendor/'
@@ -100,6 +101,10 @@ unit-race:
 	@$(call print, "Running unit race tests.")
 	env CGO_ENABLED=1 GORACE="history_size=7 halt_on_errors=1" $(UNIT_RACE)
 
+fuzz:
+	@$(call print, "Running fuzz tests.")
+	$(GOFUZZ) FuzzWitnessSpendDetection ./poolscript
+
 # =============
 # FLAKE HUNTING
 # =============

poolscript/script_test.go

@@ -89,3 +89,25 @@ func TestIncrementBatchKey(t *testing.T) {
 
 	require.Equal(t, startBatchKey, currentKey)
 }
+
+// FuzzWitnessSpendDetection fuzz tests the witness spend detection functions.
+func FuzzWitnessSpendDetection(f *testing.F) {
+	f.Fuzz(func(t *testing.T, a, b, c, d []byte, num uint8) {
+		witness := make([][]byte, num)
+
+		if num > 0 {
+			witness[0] = a
+		}
+		if num > 1 {
+			witness[1] = b
+		}
+		if num > 2 {
+			witness[2] = c
+		}
+		if num > 3 {
+			witness[3] = d
+		}
+		_ = IsMultiSigSpend(witness)
+		_ = IsExpirySpend(witness)
+	})
+}