You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: match_test.go
    path of file: ./repos/istio/pilot/pkg/networking/core/v1alpha3/match
    
    the code of the file until where you have to start completion: package match

// Copyright Istio Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import (
	"testing"

	matcher "github.com/cncf/xds/go/xds/type/matcher/v
    
func TestCleanupEmptyMaps(t *testing.T) {
	tc := []struct {
		name  string
		given func() Mapper
		want  func() *matcher.Matcher
	}{
		{
			name: "empty map at depth = 0",
			given: func() Mapper {
				// root (dest port):
				//   <no matches>
				//   fallback (dest ip):
				//     1.2.3.4: chain
				fallback := NewDestinationIP()
				fallback.Map["1.2.3.4"] = ToChain("chain")

				root := NewDestinationPort()
				root.OnNoMatch = ToMatcher(fallback.Matcher)
				return root
			},
			want: func() *matcher.Matcher {
				// root (dest ip):
				//   1.2.3.4: chain

				// fallback becomes root
				want := NewDestinationIP()
				want.Map["1.2.3.4"] = ToChain("chain")
				return want.Matcher
			},
		},
		{
			name: "empty map at depth = 1",
			given: func() Mapper {
				// root (dest port)
				//   15001:
				//     inner (dest ip):
				//       <no matches>
				//       fallback: chain
				inner := NewDestinationIP()
				inner.OnNoMatch = ToChain("chain")

				root := NewDestinationPort()
				root.Map["15001"] = ToMatcher(inner.Matcher)
				return root
			},
			want: func() *matcher.Matcher {
				// dest port
				// 15001: chain
				want := NewDestinationPort()
				want.Map["15001"] = ToChain("chain")
				return want.Matcher
			},
		},
		{
			name: "empty map at depth = 0 and 1",
			given: func() Mapper {
				// root (dest port)
				//   fallback:
				//     inner (dest ip):
				//       <no matches>
				//       fallback: chain
				leaf := NewSourceIP()
				leaf.Map["1.2.3.4"] = ToChain("chain")

				inner := NewDestinationIP()
				inner.OnNoMatch = ToMatcher(leaf.Matcher)

				root := NewDestinationPort()
				root.OnNoMatch = ToMatcher(inner.Matcher)
				return root
			},
			want: func() *matcher.Matcher {
				// src port
				// 15001: chain
				want := NewSourceIP()
				want.Map["1.2.3.4"] = ToChain("chain")
				return want.Matcher
			},
		},
		{
			name: "empty map at depths = 1 and 2",
			given: func() Mapper {
				// root (dest port)
				//   15001:
				//     middle (dest ip):
				//       fallback:
				//         inner (src ip):
				//           fallback: chain
				inner := NewSourceIP()
				inner.OnNoMatch = ToChain("chain")

				middle := NewDestinationIP()
				middle.OnNoMatch = ToMatcher(inner.Matcher)

				root := NewDestinationPort()
				root.Map["15001"] = ToMatcher(middle.Matcher)
				return root
			},
			want: func() *matcher.Matcher {
				// dest port
				// 15001: chain
				want := NewDestinationPort()
				want.Map["15001"] = ToChain("chain")
				return want.Matcher
			},
		},
	}

	for _, tt := range tc {
		t.Run(tt.name, func(t *testing.T) {
			got := tt.given().BuildMatcher()
			haveJSON, _ := protomarshal.ToJSONWithIndent(got, "  ")
			wantJSON, _ := protomarshal.ToJSONWithIndent(tt.want(), "  ")

			if diff := cmp.Diff(haveJSON, wantJSON, cmp.AllowUnexported()); diff != "" {
				t.Error(diff)
			}
		})
	}
}