Adding fuzzing for v3

.gitignore

@@ -0,0 +1 @@
+_fuzz/

Makefile

@@ -1,5 +1,7 @@
 GOPATH=$(shell go env GOPATH)
 GOLANGCI_LINT=$(GOPATH)/bin/golangci-lint
+GOFUZZBUILD = $(GOPATH)/bin/go-fuzz-build
+GOFUZZ = $(GOPATH)/bin/go-fuzz
 
 .PHONY: lint
 lint: $(GOLANGCI_LINT)
@@ -16,8 +18,20 @@ test-cover:
 	@echo "==> Running Tests with coverage"
 	GO111MODULE=on go test -cover .
 
+.PHONY: fuzz
+fuzz: $(GOFUZZBUILD) $(GOFUZZ)
+	@echo "==> Fuzz testing"
+	$(GOFUZZBUILD)
+	$(GOFUZZ) -workdir=_fuzz
+
 $(GOLANGCI_LINT):
 	# Install golangci-lint. The configuration for it is in the .golangci.yml
 	# file in the root of the repository
 	echo ${GOPATH}
-	curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(GOPATH)/bin v1.17.1
+	curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(GOPATH)/bin v1.17.1
+
+$(GOFUZZBUILD):
+	cd / && go get -u github.com/dvyukov/go-fuzz/go-fuzz-build
+
+$(GOFUZZ):
+	cd / && go get -u github.com/dvyukov/go-fuzz/go-fuzz github.com/dvyukov/go-fuzz/go-fuzz-dep

fuzz.go

@@ -0,0 +1,22 @@
+// +build gofuzz
+
+package semver
+
+func Fuzz(data []byte) int {
+	d := string(data)
+
+	// Test NewVersion
+	_, _ = NewVersion(d)
+
+	// Test StrictNewVersion
+	_, _ = StrictNewVersion(d)
+
+	// Test NewConstraint
+	_, _ = NewConstraint(d)
+
+	// The return value should be 0 normally, 1 if the priority in future tests
+	// should be increased, and -1 if future tests should skip passing in that
+	// data. We do not have a reason to change priority so 0 is always returned.
+	// There are example tests that do this.
+	return 0
+}