From 7328991bbaf1eb48e64968eb103071a70a7f2841 Mon Sep 17 00:00:00 2001
From: Etienne Perot <eperot@google.com>
Date: Fri, 9 Jun 2023 17:53:49 -0700
Subject: [PATCH] Add a unit test for `metricserver.sufficientlyEqualStats`.

PiperOrigin-RevId: 539219346
---
 runsc/metricserver/BUILD                |   8 +-
 runsc/metricserver/metricserver_test.go | 198 ++++++++++++++++++++++++
 2 files changed, 205 insertions(+), 1 deletion(-)
 create mode 100644 runsc/metricserver/metricserver_test.go

diff --git a/runsc/metricserver/BUILD b/runsc/metricserver/BUILD
index e171b3887..c793fabe1 100644
--- a/runsc/metricserver/BUILD
+++ b/runsc/metricserver/BUILD
@@ -1,4 +1,4 @@
-load("//tools:defs.bzl", "go_library")
+load("//tools:defs.bzl", "go_library", "go_test")
 
 package(
     default_applicable_licenses = ["//:license"],
@@ -28,3 +28,9 @@ go_library(
         "//runsc/sandbox",
     ],
 )
+
+go_test(
+    name = "metricserver_test",
+    srcs = ["metricserver_test.go"],
+    library = ":metricserver",
+)
diff --git a/runsc/metricserver/metricserver_test.go b/runsc/metricserver/metricserver_test.go
new file mode 100644
index 000000000..355850e7d
--- /dev/null
+++ b/runsc/metricserver/metricserver_test.go
@@ -0,0 +1,198 @@
+// Copyright 2023 The gVisor 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.
+
+package metricserver
+
+import (
+	"io/fs"
+	"os"
+	"syscall"
+	"testing"
+	"time"
+)
+
+type fakeFileInfo struct {
+	fs.FileInfo
+
+	modTime time.Time
+	size    int64
+	sys     any
+}
+
+func (f *fakeFileInfo) ModTime() time.Time { return f.modTime }
+
+func (f *fakeFileInfo) Size() int64 { return f.size }
+
+func (f *fakeFileInfo) Sys() any { return f.sys }
+
+// TestSufficientlyEqualStats tests sufficientlyEqualStats.
+func TestSufficientlyEqualStats(t *testing.T) {
+	now := time.Now()
+	twoHoursAgo := now.Add(-2 * time.Hour)
+	for _, test := range []struct {
+		name string
+		a, b os.FileInfo
+		want bool
+	}{
+		{
+			name: "empty",
+			a:    &fakeFileInfo{},
+			b:    &fakeFileInfo{},
+			want: true,
+		},
+		{
+			name: "different modification time",
+			a: &fakeFileInfo{
+				modTime: twoHoursAgo,
+			},
+			b: &fakeFileInfo{
+				modTime: now,
+			},
+			want: false,
+		},
+		{
+			name: "different size",
+			a: &fakeFileInfo{
+				size: 1337,
+			},
+			b: &fakeFileInfo{
+				size: 42,
+			},
+			want: false,
+		},
+		{
+			name: "same mod time and size, not a syscall.Stat_t",
+			a: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys:     struct{ foo string }{"bla"},
+			},
+			b: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys:     struct{ foo int }{42},
+			},
+			want: true,
+		},
+		{
+			name: "same mod time and size, only one is *syscall.Stat_t",
+			a: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys:     &syscall.Stat_t{},
+			},
+			b: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys:     struct{ foo string }{"blablabla"},
+			},
+			want: false,
+		},
+		{
+			name: "same mod time and size, one is *syscall.Stat_t, other is syscall.Stat_t",
+			a: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys:     &syscall.Stat_t{},
+			},
+			b: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys:     syscall.Stat_t{},
+			},
+			want: false,
+		},
+		{
+			name: "same mod time and size, two empty *syscall.Stat_t",
+			a: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys:     &syscall.Stat_t{},
+			},
+			b: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys:     &syscall.Stat_t{},
+			},
+			want: true,
+		},
+		{
+			name: "same mod time and size, different *syscall.Stat_t.Dev",
+			a: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys: &syscall.Stat_t{
+					Dev: 42,
+				},
+			},
+			b: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys: &syscall.Stat_t{
+					Dev: 43,
+				},
+			},
+			want: false,
+		},
+		{
+			name: "same mod time and size, different *syscall.Stat_t.Ino",
+			a: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys: &syscall.Stat_t{
+					Ino: 42,
+				},
+			},
+			b: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys: &syscall.Stat_t{
+					Ino: 43,
+				},
+			},
+			want: false,
+		},
+		{
+			name: "same mod time and size, same *syscall.Stat_t.{Dev,Ino}",
+			a: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys: &syscall.Stat_t{
+					Ino: 42,
+					Dev: 44,
+				},
+			},
+			b: &fakeFileInfo{
+				modTime: twoHoursAgo,
+				size:    1337,
+				sys: &syscall.Stat_t{
+					Ino: 42,
+					Dev: 44,
+				},
+			},
+			want: true,
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			got := sufficientlyEqualStats(test.a, test.b)
+			if got != test.want {
+				t.Errorf("got equal=%t want %t", got, test.want)
+			}
+			gotReverse := sufficientlyEqualStats(test.b, test.a)
+			if gotReverse != got {
+				t.Errorf("sufficientlyEqualStats(a, b) = %v yet sufficientlyEqualStats(b, a) = %v", got, gotReverse)
+			}
+		})
+	}
+}