test: Add findmnt package

When testing mounts we can use findmnt --json output to parse the output
cleanly. The package provides only ParseOutput() now, but it can be
extended later to run the findmnt command.

Author: nirs

test/integration/findmnt/findmnt.go

@@ -0,0 +1,88 @@
+//go:build integration
+
+/*
+Copyright 2025 The Kubernetes Authors 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 parse findmnt command results.
+package findmnt
+
+import (
+	"encoding/json"
+	"slices"
+)
+
+// Filesystem is a findmnt --json filesystem node. It may include children
+// filesystems.
+type Filesystem struct {
+	Target   string       `json:"target"`
+	Source   string       `json:"source"`
+	FSType   string       `json:"fstype"`
+	Options  string       `json:"options"`
+	Children []Filesystem `json:"children,omitempty"`
+}
+
+// Result if findmnt --json result.
+type Result struct {
+	Filesystems []Filesystem `json:"filesystems"`
+}
+
+// ParseOutput parse findmnt --json output.
+func ParseOutput(output []byte) (*Result, error) {
+	r := &Result{}
+	if err := json.Unmarshal(output, r); err != nil {
+		return nil, err
+	}
+	return r, nil
+}
+
+func (r *Result) Equal(other *Result) bool {
+	if r == other {
+		return true
+	}
+	if other == nil {
+		return false
+	}
+	if !slices.EqualFunc(r.Filesystems, other.Filesystems, func(a, b Filesystem) bool {
+		return a.Equal(&b)
+	}) {
+		return false
+	}
+	return true
+}
+
+func (f *Filesystem) Equal(other *Filesystem) bool {
+	if f == other {
+		return true
+	}
+	if other == nil {
+		return false
+	}
+	if f.Target != other.Target {
+		return false
+	}
+	if f.Source != other.Source {
+		return false
+	}
+	if f.FSType != other.FSType {
+		return false
+	}
+	if !slices.EqualFunc(f.Children, other.Children, func(a, b Filesystem) bool {
+		return a.Equal(&b)
+	}) {
+		return false
+	}
+	return true
+}

test/integration/findmnt/findmnt_test.go

@@ -0,0 +1,91 @@
+//go:build integration
+
+/*
+Copyright 2025 The Kubernetes Authors 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 findmnt_test
+
+import (
+	"os"
+	"testing"
+
+	"k8s.io/minikube/test/integration/findmnt"
+)
+
+func TestParseAllMounts(t *testing.T) {
+	// Output from `findmnt --json` command.
+	output, err := os.ReadFile("testdata/findmnt.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	result, err := findmnt.ParseOutput(output)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert(t, len(result.Filesystems), 1)
+
+	root := result.Filesystems[0]
+	assert(t, root.Target, "/")
+	assert(t, root.Source, "tmpfs")
+	assert(t, root.FSType, "tmpfs")
+	assert(t, root.Options, "rw,relatime,size=5469192k")
+	assert(t, len(root.Children), 20)
+
+	dev := root.Children[0]
+	assert(t, dev.Target, "/dev")
+	assert(t, dev.Source, "devtmpfs")
+	assert(t, dev.FSType, "devtmpfs")
+	assert(t, dev.Options, "rw,relatime,size=2838500k,nr_inodes=709625,mode=755")
+	assert(t, len(dev.Children), 4)
+
+	devShm := dev.Children[0]
+	assert(t, devShm.Target, "/dev/shm")
+	assert(t, devShm.Source, "tmpfs")
+	assert(t, devShm.FSType, "tmpfs")
+	assert(t, devShm.Options, "rw,nosuid,nodev")
+}
+
+func TestParseSingle(t *testing.T) {
+	// Output from `findmnt --json /proc` command.
+	output, err := os.ReadFile("testdata/findmnt-proc.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	result, err := findmnt.ParseOutput(output)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := &findmnt.Result{
+		Filesystems: []findmnt.Filesystem{
+			{
+				Target:  "/proc",
+				Source:  "proc",
+				FSType:  "proc",
+				Options: "rw,relatime",
+			},
+		},
+	}
+	if !result.Equal(expected) {
+		t.Fatalf("expected %+v, got %+v", expected, result)
+	}
+}
+
+func assert[T comparable](t *testing.T, a, b T) {
+	if a != b {
+		t.Fatalf("expected \"%v\", got \"%v\"", b, a)
+	}
+}

test/integration/findmnt/testdata/findmnt-proc.json

@@ -0,0 +1,10 @@
+{
+   "filesystems": [
+      {
+         "target": "/proc",
+         "source": "proc",
+         "fstype": "proc",
+         "options": "rw,relatime"
+      }
+   ]
+}