Adding fuzzing for v3

.gitignore

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

Makefile

@@ -16,6 +16,12 @@ test-cover:
 	@echo "==> Running Tests with coverage"
 	GO111MODULE=on go test -cover .
 
+.PHONY: fuzz
+fuzz:
+	@echo "==> Fuzz testing"
+	go-fuzz-build
+	go-fuzz -workdir=_fuzz
+
 $(GOLANGCI_LINT):
 	# Install golangci-lint. The configuration for it is in the .golangci.yml
 	# file in the root of the repository

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
+}