Import files from compare_target_files for use in diff_target_files

Copied from cl/240594925.

Bug: 121158314
Test: copied unit tests
Change-Id: I2e91126285dcd33171ff8b8dbfcfa5d48501f535
diff --git a/cmd/diff_target_files/compare_test.go b/cmd/diff_target_files/compare_test.go
new file mode 100644
index 0000000..9d3f8a5
--- /dev/null
+++ b/cmd/diff_target_files/compare_test.go
@@ -0,0 +1,131 @@
+// Copyright 2019 Google Inc. All rights reserved.
+//
+// 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.
+
+package main
+
+import (
+	"archive/zip"
+	"reflect"
+	"testing"
+)
+
+func TestDiffTargetFilesLists(t *testing.T) {
+	zipArtifactFile := func(name string, crc32 uint32, size uint64) *ZipArtifactFile {
+		return &ZipArtifactFile{
+			File: &zip.File{
+				FileHeader: zip.FileHeader{
+					Name:               name,
+					CRC32:              crc32,
+					UncompressedSize64: size,
+				},
+			},
+		}
+	}
+	x0 := zipArtifactFile("x", 0, 0)
+	x1 := zipArtifactFile("x", 1, 0)
+	x2 := zipArtifactFile("x", 0, 2)
+	y0 := zipArtifactFile("y", 0, 0)
+	//y1 := zipArtifactFile("y", 1, 0)
+	//y2 := zipArtifactFile("y", 1, 2)
+	z0 := zipArtifactFile("z", 0, 0)
+	z1 := zipArtifactFile("z", 1, 0)
+	//z2 := zipArtifactFile("z", 1, 2)
+
+	testCases := []struct {
+		name string
+		a, b []*ZipArtifactFile
+		diff zipDiff
+	}{
+		{
+			name: "same",
+			a:    []*ZipArtifactFile{x0, y0, z0},
+			b:    []*ZipArtifactFile{x0, y0, z0},
+			diff: zipDiff{nil, nil, nil},
+		},
+		{
+			name: "first only in a",
+			a:    []*ZipArtifactFile{x0, y0, z0},
+			b:    []*ZipArtifactFile{y0, z0},
+			diff: zipDiff{nil, []*ZipArtifactFile{x0}, nil},
+		},
+		{
+			name: "middle only in a",
+			a:    []*ZipArtifactFile{x0, y0, z0},
+			b:    []*ZipArtifactFile{x0, z0},
+			diff: zipDiff{nil, []*ZipArtifactFile{y0}, nil},
+		},
+		{
+			name: "last only in a",
+			a:    []*ZipArtifactFile{x0, y0, z0},
+			b:    []*ZipArtifactFile{x0, y0},
+			diff: zipDiff{nil, []*ZipArtifactFile{z0}, nil},
+		},
+
+		{
+			name: "first only in b",
+			a:    []*ZipArtifactFile{y0, z0},
+			b:    []*ZipArtifactFile{x0, y0, z0},
+			diff: zipDiff{nil, nil, []*ZipArtifactFile{x0}},
+		},
+		{
+			name: "middle only in b",
+			a:    []*ZipArtifactFile{x0, z0},
+			b:    []*ZipArtifactFile{x0, y0, z0},
+			diff: zipDiff{nil, nil, []*ZipArtifactFile{y0}},
+		},
+		{
+			name: "last only in b",
+			a:    []*ZipArtifactFile{x0, y0},
+			b:    []*ZipArtifactFile{x0, y0, z0},
+			diff: zipDiff{nil, nil, []*ZipArtifactFile{z0}},
+		},
+
+		{
+			name: "diff",
+			a:    []*ZipArtifactFile{x0},
+			b:    []*ZipArtifactFile{x1},
+			diff: zipDiff{[][2]*ZipArtifactFile{{x0, x1}}, nil, nil},
+		},
+		{
+			name: "diff plus unique last",
+			a:    []*ZipArtifactFile{x0, y0},
+			b:    []*ZipArtifactFile{x1, z0},
+			diff: zipDiff{[][2]*ZipArtifactFile{{x0, x1}}, []*ZipArtifactFile{y0}, []*ZipArtifactFile{z0}},
+		},
+		{
+			name: "diff plus unique first",
+			a:    []*ZipArtifactFile{x0, z0},
+			b:    []*ZipArtifactFile{y0, z1},
+			diff: zipDiff{[][2]*ZipArtifactFile{{z0, z1}}, []*ZipArtifactFile{x0}, []*ZipArtifactFile{y0}},
+		},
+		{
+			name: "diff size",
+			a:    []*ZipArtifactFile{x0},
+			b:    []*ZipArtifactFile{x2},
+			diff: zipDiff{[][2]*ZipArtifactFile{{x0, x2}}, nil, nil},
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.name, func(t *testing.T) {
+			diff := diffTargetFilesLists(test.a, test.b)
+
+			if !reflect.DeepEqual(diff, test.diff) {
+
+				t.Errorf("diffTargetFilesLists = %v, %v, %v", diff.modified, diff.onlyInA, diff.onlyInB)
+				t.Errorf("                  want %v, %v, %v", test.diff.modified, test.diff.onlyInA, test.diff.onlyInB)
+			}
+		})
+	}
+}