diff --git a/.golangci.yml b/.golangci.yml
index 2b51128..e74f4ad 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -472,4 +472,5 @@ linters:
           - goconst
           - gosec
           - noctx
+          - reassign
           - wrapcheck
diff --git a/tee/tee.go b/tee/tee.go
index 1d7a1f0..00faf8e 100644
--- a/tee/tee.go
+++ b/tee/tee.go
@@ -17,23 +17,6 @@ type Tee struct {
 	Verbose bool
 }
 
-func (t *Tee) Write(p []byte) (int, error) {
-	n, err := os.Stdout.Write(p)
-	if err != nil {
-		return n, err
-	}
-
-	if t.f != nil {
-		return t.f.Write(p)
-	}
-	return n, nil
-}
-
-// Close calls Close on the underlying file.
-func (t *Tee) Close() error {
-	return t.f.Close()
-}
-
 // NewOut writes to standard output only. The file is created, not
 // appended to.
 func NewOut(logFile string) (*Tee, error) {
@@ -48,9 +31,32 @@ func NewOut(logFile string) (*Tee, error) {
 	return &Tee{f: f}, nil
 }
 
+func (t *Tee) Write(p []byte) (int, error) {
+	n, err := os.Stdout.Write(p)
+	if err != nil {
+		return n, err
+	}
+
+	if t.f != nil {
+		return t.f.Write(p)
+	}
+	return n, nil
+}
+
+// Close calls Close on the underlying file if present.
+// It is safe to call Close on a Tee with no file; in that case, it returns nil.
+func (t *Tee) Close() error {
+	if t == nil || t.f == nil {
+		return nil
+	}
+	err := t.f.Close()
+	t.f = nil
+	return err
+}
+
 // Printf formats according to a format specifier and writes to the
 // tee instance.
-func (t *Tee) Printf(format string, args ...interface{}) (int, error) {
+func (t *Tee) Printf(format string, args ...any) (int, error) {
 	s := fmt.Sprintf(format, args...)
 	n, err := os.Stdout.WriteString(s)
 	if err != nil {
@@ -66,7 +72,7 @@ func (t *Tee) Printf(format string, args ...interface{}) (int, error) {
 
 // VPrintf is a variant of Printf that only prints if the Tee's
 // Verbose flag is set.
-func (t *Tee) VPrintf(format string, args ...interface{}) (int, error) {
+func (t *Tee) VPrintf(format string, args ...any) (int, error) {
 	if t.Verbose {
 		return t.Printf(format, args...)
 	}
@@ -87,12 +93,12 @@ func Open(logFile string) error {
 
 // Printf formats according to a format specifier and writes to the
 // global tee.
-func Printf(format string, args ...interface{}) (int, error) {
+func Printf(format string, args ...any) (int, error) {
 	return globalTee.Printf(format, args...)
 }
 
 // VPrintf calls VPrintf on the global tee instance.
-func VPrintf(format string, args ...interface{}) (int, error) {
+func VPrintf(format string, args ...any) (int, error) {
 	return globalTee.VPrintf(format, args...)
 }
 
diff --git a/tee/tee_test.go b/tee/tee_test.go
new file mode 100644
index 0000000..4813885
--- /dev/null
+++ b/tee/tee_test.go
@@ -0,0 +1,197 @@
+package tee_test
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"testing"
+
+	tee "git.wntrmute.dev/kyle/goutils/tee"
+)
+
+// captureStdout redirects os.Stdout for the duration of fn and returns what was written.
+func captureStdout(t *testing.T, fn func()) string {
+	t.Helper()
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("pipe: %v", err)
+	}
+	old := os.Stdout
+	os.Stdout = w
+	defer func() { os.Stdout = old }()
+
+	fn()
+
+	// Close writer to unblock reader and restore stdout
+	_ = w.Close()
+	b, _ := io.ReadAll(r)
+	_ = r.Close()
+	return string(b)
+}
+
+func TestNewOutEmpty_WritesToStdoutOnly(t *testing.T) {
+	teeInst, err := tee.NewOut("")
+	if err != nil {
+		t.Fatalf("NewOut: %v", err)
+	}
+
+	out := captureStdout(t, func() {
+		var n int
+		if n, err = teeInst.Write([]byte("abc")); err != nil || n != 3 {
+			t.Fatalf("Write got n=%d err=%v", n, err)
+		}
+
+		if n, err = teeInst.Printf("-%d-", 7); err != nil || n != len("-7-") {
+			t.Fatalf("Printf got n=%d err=%v", n, err)
+		}
+	})
+
+	if out != "abc-7-" {
+		t.Fatalf("stdout = %q, want %q", out, "abc-7-")
+	}
+}
+
+func TestNewOutWithFile_WritesToBoth(t *testing.T) {
+	dir := t.TempDir()
+	logPath := filepath.Join(dir, "log.txt")
+
+	teeInst, err := tee.NewOut(logPath)
+	if err != nil {
+		t.Fatalf("NewOut: %v", err)
+	}
+	defer func() { _ = teeInst.Close() }()
+
+	out := captureStdout(t, func() {
+		if _, err = teeInst.Write([]byte("x")); err != nil {
+			t.Fatalf("Write: %v", err)
+		}
+		if _, err = teeInst.Printf("%s", "y"); err != nil {
+			t.Fatalf("Printf: %v", err)
+		}
+	})
+
+	if out != "xy" {
+		t.Fatalf("stdout = %q, want %q", out, "xy")
+	}
+
+	// Close to flush and release the file before reading
+	if err = teeInst.Close(); err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+
+	data, err := os.ReadFile(logPath)
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	if string(data) != "xy" {
+		t.Fatalf("file content = %q, want %q", string(data), "xy")
+	}
+}
+
+func TestVPrintf_VerboseToggle(t *testing.T) {
+	teeInst := &tee.Tee{} // stdout only
+
+	out := captureStdout(t, func() {
+		if n, err := teeInst.VPrintf("hello"); err != nil || n != 0 {
+			t.Fatalf("VPrintf (quiet) got n=%d err=%v", n, err)
+		}
+	})
+	if out != "" {
+		t.Fatalf("stdout = %q, want empty when not verbose", out)
+	}
+
+	teeInst.Verbose = true
+	out = captureStdout(t, func() {
+		if n, err := teeInst.VPrintf("%s", "hello"); err != nil || n != len("hello") {
+			t.Fatalf("VPrintf (verbose) got n=%d err=%v", n, err)
+		}
+	})
+	if out != "hello" {
+		t.Fatalf("stdout = %q, want %q", out, "hello")
+	}
+}
+
+func TestWrite_StdoutErrorDoesNotWriteToFile(t *testing.T) {
+	dir := t.TempDir()
+	logPath := filepath.Join(dir, "log.txt")
+	teeInst, err := tee.NewOut(logPath)
+	if err != nil {
+		t.Fatalf("NewOut: %v", err)
+	}
+	defer func() { _ = teeInst.Close() }()
+
+	// Replace stdout with a closed pipe writer to force write error.
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("pipe: %v", err)
+	}
+	old := os.Stdout
+	os.Stdout = w
+	_ = w.Close() // immediately close to cause EPIPE on write
+	defer func() {
+		os.Stdout = old
+		_ = r.Close()
+	}()
+
+	var n int
+	if n, err = teeInst.Write([]byte("abc")); err == nil {
+		t.Fatalf("expected error writing to closed stdout, got n=%d err=nil", n)
+	}
+
+	// Ensure file remained empty because stdout write failed first.
+	_ = teeInst.Close()
+	data, err := os.ReadFile(logPath)
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	if len(data) != 0 {
+		t.Fatalf("file content = %q, want empty due to stdout failure", string(data))
+	}
+}
+
+func TestGlobal_OpenPrintfVPrintfClose(t *testing.T) {
+	// Ensure a clean slate for global tee
+	_ = tee.Close()
+	tee.SetVerbose(false)
+
+	dir := t.TempDir()
+	logPath := filepath.Join(dir, "glog.txt")
+
+	if err := tee.Open(logPath); err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+
+	out := captureStdout(t, func() {
+		if _, err := tee.Printf("A"); err != nil {
+			t.Fatalf("Printf: %v", err)
+		}
+		// Not verbose yet, should not print
+		if n, err := tee.VPrintf("B"); err != nil || n != 0 {
+			t.Fatalf("VPrintf (quiet) n=%d err=%v", n, err)
+		}
+		tee.SetVerbose(true)
+		if _, err := tee.VPrintf("C%d", 1); err != nil {
+			t.Fatalf("VPrintf (verbose): %v", err)
+		}
+	})
+
+	if out != "AC1" {
+		t.Fatalf("stdout = %q, want %q", out, "AC1")
+	}
+
+	if err := tee.Close(); err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+
+	data, err := os.ReadFile(logPath)
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	if string(data) != "AC1" {
+		t.Fatalf("file content = %q, want %q", string(data), "AC1")
+	}
+
+	// Reset global tee for other tests/packages
+	_ = tee.Close()
+	tee.SetVerbose(false)
+}