@@ -0,0 +1,483 @@
+package fsext
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/charmbracelet/crush/internal/home"
+	"github.com/stretchr/testify/require"
+)
+
+func TestLookupClosest(t *testing.T) {
+	tempDir := t.TempDir()
+
+	// Change to temp directory
+	oldWd, _ := os.Getwd()
+	err := os.Chdir(tempDir)
+	require.NoError(t, err)
+
+	t.Cleanup(func() {
+		os.Chdir(oldWd)
+	})
+
+	t.Run("target found in starting directory", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create target file in current directory
+		targetFile := filepath.Join(testDir, "target.txt")
+		err := os.WriteFile(targetFile, []byte("test"), 0o644)
+		require.NoError(t, err)
+
+		foundPath, found := LookupClosest(testDir, "target.txt")
+		require.True(t, found)
+		require.Equal(t, targetFile, foundPath)
+	})
+
+	t.Run("target found in parent directory", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create subdirectory
+		subDir := filepath.Join(testDir, "subdir")
+		err := os.Mkdir(subDir, 0o755)
+		require.NoError(t, err)
+
+		// Create target file in parent directory
+		targetFile := filepath.Join(testDir, "target.txt")
+		err = os.WriteFile(targetFile, []byte("test"), 0o644)
+		require.NoError(t, err)
+
+		foundPath, found := LookupClosest(subDir, "target.txt")
+		require.True(t, found)
+		require.Equal(t, targetFile, foundPath)
+	})
+
+	t.Run("target found in grandparent directory", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create nested subdirectories
+		subDir := filepath.Join(testDir, "subdir")
+		err := os.Mkdir(subDir, 0o755)
+		require.NoError(t, err)
+
+		subSubDir := filepath.Join(subDir, "subsubdir")
+		err = os.Mkdir(subSubDir, 0o755)
+		require.NoError(t, err)
+
+		// Create target file in grandparent directory
+		targetFile := filepath.Join(testDir, "target.txt")
+		err = os.WriteFile(targetFile, []byte("test"), 0o644)
+		require.NoError(t, err)
+
+		foundPath, found := LookupClosest(subSubDir, "target.txt")
+		require.True(t, found)
+		require.Equal(t, targetFile, foundPath)
+	})
+
+	t.Run("target not found", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		foundPath, found := LookupClosest(testDir, "nonexistent.txt")
+		require.False(t, found)
+		require.Empty(t, foundPath)
+	})
+
+	t.Run("target directory found", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create target directory in current directory
+		targetDir := filepath.Join(testDir, "targetdir")
+		err := os.Mkdir(targetDir, 0o755)
+		require.NoError(t, err)
+
+		foundPath, found := LookupClosest(testDir, "targetdir")
+		require.True(t, found)
+		require.Equal(t, targetDir, foundPath)
+	})
+
+	t.Run("stops at home directory", func(t *testing.T) {
+		// This test is limited as we can't easily create files above home directory
+		// but we can test the behavior by searching from home directory itself
+		homeDir := home.Dir()
+
+		// Search for a file that doesn't exist from home directory
+		foundPath, found := LookupClosest(homeDir, "nonexistent_file_12345.txt")
+		require.False(t, found)
+		require.Empty(t, foundPath)
+	})
+
+	t.Run("invalid starting directory", func(t *testing.T) {
+		foundPath, found := LookupClosest("/invalid/path/that/does/not/exist", "target.txt")
+		require.False(t, found)
+		require.Empty(t, foundPath)
+	})
+
+	t.Run("relative path handling", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Change to test directory
+		oldWd, _ := os.Getwd()
+		err := os.Chdir(testDir)
+		require.NoError(t, err)
+		defer os.Chdir(oldWd)
+
+		// Create target file in current directory
+		err = os.WriteFile("target.txt", []byte("test"), 0o644)
+		require.NoError(t, err)
+
+		// Search using relative path
+		foundPath, found := LookupClosest(".", "target.txt")
+		require.True(t, found)
+
+		// Resolve symlinks to handle macOS /private/var vs /var discrepancy
+		expectedPath, err := filepath.EvalSymlinks(filepath.Join(testDir, "target.txt"))
+		require.NoError(t, err)
+		actualPath, err := filepath.EvalSymlinks(foundPath)
+		require.NoError(t, err)
+		require.Equal(t, expectedPath, actualPath)
+	})
+}
+
+func TestLookupClosestWithOwnership(t *testing.T) {
+	// Note: Testing ownership boundaries is difficult in a cross-platform way
+	// without creating complex directory structures with different owners.
+	// This test focuses on the basic functionality when ownership checks pass.
+
+	tempDir := t.TempDir()
+
+	// Change to temp directory
+	oldWd, _ := os.Getwd()
+	err := os.Chdir(tempDir)
+	require.NoError(t, err)
+
+	t.Cleanup(func() {
+		os.Chdir(oldWd)
+	})
+
+	t.Run("search respects same ownership", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create subdirectory structure
+		subDir := filepath.Join(testDir, "subdir")
+		err := os.Mkdir(subDir, 0o755)
+		require.NoError(t, err)
+
+		// Create target file in parent directory
+		targetFile := filepath.Join(testDir, "target.txt")
+		err = os.WriteFile(targetFile, []byte("test"), 0o644)
+		require.NoError(t, err)
+
+		// Search should find the target assuming same ownership
+		foundPath, found := LookupClosest(subDir, "target.txt")
+		require.True(t, found)
+		require.Equal(t, targetFile, foundPath)
+	})
+}
+
+func TestLookup(t *testing.T) {
+	tempDir := t.TempDir()
+
+	// Change to temp directory
+	oldWd, _ := os.Getwd()
+	err := os.Chdir(tempDir)
+	require.NoError(t, err)
+
+	t.Cleanup(func() {
+		os.Chdir(oldWd)
+	})
+
+	t.Run("no targets returns empty slice", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		found, err := Lookup(testDir)
+		require.NoError(t, err)
+		require.Empty(t, found)
+	})
+
+	t.Run("single target found in starting directory", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create target file in current directory
+		targetFile := filepath.Join(testDir, "target.txt")
+		err := os.WriteFile(targetFile, []byte("test"), 0o644)
+		require.NoError(t, err)
+
+		found, err := Lookup(testDir, "target.txt")
+		require.NoError(t, err)
+		require.Len(t, found, 1)
+		require.Equal(t, targetFile, found[0])
+	})
+
+	t.Run("multiple targets found in starting directory", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create multiple target files in current directory
+		targetFile1 := filepath.Join(testDir, "target1.txt")
+		targetFile2 := filepath.Join(testDir, "target2.txt")
+		targetFile3 := filepath.Join(testDir, "target3.txt")
+
+		err := os.WriteFile(targetFile1, []byte("test1"), 0o644)
+		require.NoError(t, err)
+		err = os.WriteFile(targetFile2, []byte("test2"), 0o644)
+		require.NoError(t, err)
+		err = os.WriteFile(targetFile3, []byte("test3"), 0o644)
+		require.NoError(t, err)
+
+		found, err := Lookup(testDir, "target1.txt", "target2.txt", "target3.txt")
+		require.NoError(t, err)
+		require.Len(t, found, 3)
+		require.Contains(t, found, targetFile1)
+		require.Contains(t, found, targetFile2)
+		require.Contains(t, found, targetFile3)
+	})
+
+	t.Run("targets found in parent directories", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create subdirectory
+		subDir := filepath.Join(testDir, "subdir")
+		err := os.Mkdir(subDir, 0o755)
+		require.NoError(t, err)
+
+		// Create target files in parent directory
+		targetFile1 := filepath.Join(testDir, "target1.txt")
+		targetFile2 := filepath.Join(testDir, "target2.txt")
+		err = os.WriteFile(targetFile1, []byte("test1"), 0o644)
+		require.NoError(t, err)
+		err = os.WriteFile(targetFile2, []byte("test2"), 0o644)
+		require.NoError(t, err)
+
+		found, err := Lookup(subDir, "target1.txt", "target2.txt")
+		require.NoError(t, err)
+		require.Len(t, found, 2)
+		require.Contains(t, found, targetFile1)
+		require.Contains(t, found, targetFile2)
+	})
+
+	t.Run("targets found across multiple directory levels", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create nested subdirectories
+		subDir := filepath.Join(testDir, "subdir")
+		err := os.Mkdir(subDir, 0o755)
+		require.NoError(t, err)
+
+		subSubDir := filepath.Join(subDir, "subsubdir")
+		err = os.Mkdir(subSubDir, 0o755)
+		require.NoError(t, err)
+
+		// Create target files at different levels
+		targetFile1 := filepath.Join(testDir, "target1.txt")
+		targetFile2 := filepath.Join(subDir, "target2.txt")
+		targetFile3 := filepath.Join(subSubDir, "target3.txt")
+
+		err = os.WriteFile(targetFile1, []byte("test1"), 0o644)
+		require.NoError(t, err)
+		err = os.WriteFile(targetFile2, []byte("test2"), 0o644)
+		require.NoError(t, err)
+		err = os.WriteFile(targetFile3, []byte("test3"), 0o644)
+		require.NoError(t, err)
+
+		found, err := Lookup(subSubDir, "target1.txt", "target2.txt", "target3.txt")
+		require.NoError(t, err)
+		require.Len(t, found, 3)
+		require.Contains(t, found, targetFile1)
+		require.Contains(t, found, targetFile2)
+		require.Contains(t, found, targetFile3)
+	})
+
+	t.Run("some targets not found", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create only some target files
+		targetFile1 := filepath.Join(testDir, "target1.txt")
+		targetFile2 := filepath.Join(testDir, "target2.txt")
+
+		err := os.WriteFile(targetFile1, []byte("test1"), 0o644)
+		require.NoError(t, err)
+		err = os.WriteFile(targetFile2, []byte("test2"), 0o644)
+		require.NoError(t, err)
+
+		// Search for existing and non-existing targets
+		found, err := Lookup(testDir, "target1.txt", "nonexistent.txt", "target2.txt", "another_nonexistent.txt")
+		require.NoError(t, err)
+		require.Len(t, found, 2)
+		require.Contains(t, found, targetFile1)
+		require.Contains(t, found, targetFile2)
+	})
+
+	t.Run("no targets found", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		found, err := Lookup(testDir, "nonexistent1.txt", "nonexistent2.txt", "nonexistent3.txt")
+		require.NoError(t, err)
+		require.Empty(t, found)
+	})
+
+	t.Run("target directories found", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create target directories
+		targetDir1 := filepath.Join(testDir, "targetdir1")
+		targetDir2 := filepath.Join(testDir, "targetdir2")
+		err := os.Mkdir(targetDir1, 0o755)
+		require.NoError(t, err)
+		err = os.Mkdir(targetDir2, 0o755)
+		require.NoError(t, err)
+
+		found, err := Lookup(testDir, "targetdir1", "targetdir2")
+		require.NoError(t, err)
+		require.Len(t, found, 2)
+		require.Contains(t, found, targetDir1)
+		require.Contains(t, found, targetDir2)
+	})
+
+	t.Run("mixed files and directories", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Create target files and directories
+		targetFile := filepath.Join(testDir, "target.txt")
+		targetDir := filepath.Join(testDir, "targetdir")
+		err := os.WriteFile(targetFile, []byte("test"), 0o644)
+		require.NoError(t, err)
+		err = os.Mkdir(targetDir, 0o755)
+		require.NoError(t, err)
+
+		found, err := Lookup(testDir, "target.txt", "targetdir")
+		require.NoError(t, err)
+		require.Len(t, found, 2)
+		require.Contains(t, found, targetFile)
+		require.Contains(t, found, targetDir)
+	})
+
+	t.Run("invalid starting directory", func(t *testing.T) {
+		found, err := Lookup("/invalid/path/that/does/not/exist", "target.txt")
+		require.Error(t, err)
+		require.Empty(t, found)
+	})
+
+	t.Run("relative path handling", func(t *testing.T) {
+		testDir := t.TempDir()
+
+		// Change to test directory
+		oldWd, _ := os.Getwd()
+		err := os.Chdir(testDir)
+		require.NoError(t, err)
+
+		t.Cleanup(func() {
+			os.Chdir(oldWd)
+		})
+
+		// Create target files in current directory
+		err = os.WriteFile("target1.txt", []byte("test1"), 0o644)
+		require.NoError(t, err)
+		err = os.WriteFile("target2.txt", []byte("test2"), 0o644)
+		require.NoError(t, err)
+
+		// Search using relative path
+		found, err := Lookup(".", "target1.txt", "target2.txt")
+		require.NoError(t, err)
+		require.Len(t, found, 2)
+
+		// Resolve symlinks to handle macOS /private/var vs /var discrepancy
+		expectedPath1, err := filepath.EvalSymlinks(filepath.Join(testDir, "target1.txt"))
+		require.NoError(t, err)
+		expectedPath2, err := filepath.EvalSymlinks(filepath.Join(testDir, "target2.txt"))
+		require.NoError(t, err)
+
+		// Check that found paths match expected paths (order may vary)
+		foundEvalSymlinks := make([]string, len(found))
+		for i, path := range found {
+			evalPath, err := filepath.EvalSymlinks(path)
+			require.NoError(t, err)
+			foundEvalSymlinks[i] = evalPath
+		}
+
+		require.Contains(t, foundEvalSymlinks, expectedPath1)
+		require.Contains(t, foundEvalSymlinks, expectedPath2)
+	})
+}
+
+func TestProbeEnt(t *testing.T) {
+	t.Run("existing file with correct owner", func(t *testing.T) {
+		tempDir := t.TempDir()
+
+		// Create test file
+		testFile := filepath.Join(tempDir, "test.txt")
+		err := os.WriteFile(testFile, []byte("test"), 0o644)
+		require.NoError(t, err)
+
+		// Get owner of temp directory
+		owner, err := Owner(tempDir)
+		require.NoError(t, err)
+
+		// Test probeEnt with correct owner
+		err = probeEnt(testFile, owner)
+		require.NoError(t, err)
+	})
+
+	t.Run("existing directory with correct owner", func(t *testing.T) {
+		tempDir := t.TempDir()
+
+		// Create test directory
+		testDir := filepath.Join(tempDir, "testdir")
+		err := os.Mkdir(testDir, 0o755)
+		require.NoError(t, err)
+
+		// Get owner of temp directory
+		owner, err := Owner(tempDir)
+		require.NoError(t, err)
+
+		// Test probeEnt with correct owner
+		err = probeEnt(testDir, owner)
+		require.NoError(t, err)
+	})
+
+	t.Run("nonexistent file", func(t *testing.T) {
+		tempDir := t.TempDir()
+
+		nonexistentFile := filepath.Join(tempDir, "nonexistent.txt")
+		owner, err := Owner(tempDir)
+		require.NoError(t, err)
+
+		err = probeEnt(nonexistentFile, owner)
+		require.Error(t, err)
+		require.True(t, errors.Is(err, os.ErrNotExist))
+	})
+
+	t.Run("nonexistent file in nonexistent directory", func(t *testing.T) {
+		nonexistentFile := "/this/directory/does/not/exists/nonexistent.txt"
+
+		err := probeEnt(nonexistentFile, -1)
+		require.Error(t, err)
+		require.True(t, errors.Is(err, os.ErrNotExist))
+	})
+
+	t.Run("ownership bypass with -1", func(t *testing.T) {
+		tempDir := t.TempDir()
+
+		// Create test file
+		testFile := filepath.Join(tempDir, "test.txt")
+		err := os.WriteFile(testFile, []byte("test"), 0o644)
+		require.NoError(t, err)
+
+		// Test probeEnt with -1 (bypass ownership check)
+		err = probeEnt(testFile, -1)
+		require.NoError(t, err)
+	})
+
+	t.Run("ownership mismatch returns permission error", func(t *testing.T) {
+		tempDir := t.TempDir()
+
+		// Create test file
+		testFile := filepath.Join(tempDir, "test.txt")
+		err := os.WriteFile(testFile, []byte("test"), 0o644)
+		require.NoError(t, err)
+
+		// Test probeEnt with different owner (use 9999 which is unlikely to be the actual owner)
+		err = probeEnt(testFile, 9999)
+		require.Error(t, err)
+		require.True(t, errors.Is(err, os.ErrPermission))
+	})
+}