Add first fuzzing test (#94)

Makefile

@@ -30,6 +30,10 @@ benchstat:
 test:
 	CGO_ENABLED=1 $(GO) test ./... -coverprofile=coverage.out -covermode=atomic && go tool cover -func=coverage.out
 
+.PHONY: fuzz
+fuzz:
+	CGO_ENABLED=1 $(GO) test -fuzz=Fuzz -v -run ^Fuzz github.com/metal-stack/go-ipam 
+
 .PHONY: golangcicheck
 golangcicheck:
 	@/bin/bash -c "type -P golangci-lint;" 2>/dev/null || (echo "golangci-lint is required but not available in current PATH. Install: https://github.com/golangci/golangci-lint#install"; exit 1)

prefix_fuzz_test.go

@@ -0,0 +1,64 @@
+package ipam
+
+import (
+	"context"
+	"net/netip"
+	"testing"
+)
+
+func FuzzIpamer_AcquireIP(f *testing.F) {
+	ctx := context.Background()
+	tests := []struct {
+		name       string
+		prefixCIDR string
+		want       string
+	}{
+		{
+			name:       "Acquire next IP regularly",
+			prefixCIDR: "192.168.1.0/24",
+			want:       "192.168.1.1",
+		},
+		{
+			name:       "Acquire next IPv6 regularly",
+			prefixCIDR: "2001:db8:85a3::/124",
+			want:       "2001:db8:85a3::1",
+		},
+		{
+			name:       "Want next IP, but network is full",
+			prefixCIDR: "192.168.4.0/32",
+			want:       "",
+		},
+		{
+			name:       "Want next IPv6, but network is full",
+			prefixCIDR: "2001:db8:85a3::/128",
+			want:       "",
+		},
+	}
+	for _, tc := range tests {
+		tc := tc
+		f.Add(tc.prefixCIDR, tc.want)
+	}
+
+	f.Fuzz(func(t *testing.T, prefixCIDR, want string) {
+		ipam := New()
+		p, err := ipam.NewPrefix(ctx, prefixCIDR)
+
+		if err == nil {
+			prefix, err := netip.ParsePrefix(prefixCIDR)
+			if err != nil {
+				t.Errorf(err.Error())
+			}
+			if prefix.Masked().String() != p.String() {
+				if err != nil {
+					t.Errorf("%q not equal %q", prefix.Masked().String(), p.String())
+				}
+			}
+			ip, err := ipam.AcquireIP(ctx, p.Cidr)
+			if err == nil && want != "" && want != ip.IP.String() {
+				if err != nil {
+					t.Errorf("%q not equal %q", want, ip.IP.String())
+				}
+			}
+		}
+	})
+}

testdata/fuzz/FuzzIpamer_AcquireIP/00e15d22123489fd226477045221a413abf1174857875133adc429e5e59623f1

@@ -0,0 +1,3 @@
+go test fuzz v1
+string("0")
+string("0")