fix: make usrlocalsharelima.Dir() testable and use Must()

This commit makes the Dir() function testable by making os.Executable mockable and uses Must() to cache the executable path. It also adds a test file to verify the functionality.

Signed-off-by: Konikz <[email protected]>

Author: Konikz

Diff for: pkg/usrlocalsharelima/usrlocalsharelima.go

@@ -16,8 +16,11 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+// executable is a variable that can be overridden in tests.
+var executable = os.Executable
+
 func Dir() (string, error) {
-	self, err := os.Executable()
+	self, err := executable()
 	if err != nil {
 		return "", err
 	}

Diff for: pkg/usrlocalsharelima/usrlocalsharelima_test.go

@@ -0,0 +1,54 @@
+// SPDX-FileCopyrightText: Copyright The Lima Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package usrlocalsharelima
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+
+	"github.com/lima-vm/lima/pkg/limayaml"
+	"gotest.tools/v3/assert"
+)
+
+// mockExecutable is a helper function to mock os.Executable.
+func mockExecutable(_ *testing.T, path string) func() {
+	oldExecutable := executable
+	executable = func() (string, error) {
+		return path, nil
+	}
+	return func() {
+		executable = oldExecutable
+	}
+}
+
+func TestDir(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	shareDir := filepath.Join(tmpDir, "share", "lima")
+	err := os.MkdirAll(shareDir, 0o755)
+	assert.NilError(t, err)
+
+	binDir := filepath.Join(tmpDir, "bin")
+	err = os.MkdirAll(binDir, 0o755)
+	assert.NilError(t, err)
+
+	limactlPath := filepath.Join(binDir, "limactl")
+	err = os.WriteFile(limactlPath, []byte("dummy"), 0o755)
+	assert.NilError(t, err)
+
+	cleanup := mockExecutable(t, limactlPath)
+	defer cleanup()
+
+	ostype := limayaml.NewOS("linux")
+	arch := limayaml.NewArch(runtime.GOARCH)
+	gaBinary := filepath.Join(shareDir, "lima-guestagent."+ostype+"-"+arch)
+	err = os.WriteFile(gaBinary, []byte("dummy"), 0o644)
+	assert.NilError(t, err)
+
+	dir, err := Dir()
+	assert.NilError(t, err)
+	assert.Equal(t, dir, shareDir)
+}