diff --git a/internal/verbose/print_test.go b/internal/verbose/print_test.go
new file mode 100644
index 0000000..010557a
--- /dev/null
+++ b/internal/verbose/print_test.go
@@ -0,0 +1,67 @@
+package verbose_test
+
+import (
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"testing"
+
+	"git.ophivana.moe/cat/fortify/internal/verbose"
+)
+
+const (
+	testVerbose = "GO_TEST_VERBOSE"
+	wantStdout  = "fortify: println\nfortify: printf"
+)
+
+func TestPrinter(t *testing.T) {
+	switch os.Getenv(testVerbose) {
+	case "0":
+		verbose.Set(false)
+	case "1":
+		verbose.Set(true)
+	default:
+		return
+	}
+
+	verbose.Println("println")
+	verbose.Printf("%s", "printf")
+}
+
+func TestPrintf_Println(t *testing.T) {
+	testPrintfPrintln(t, false)
+	testPrintfPrintln(t, true)
+
+	// make -cover happy
+	stdout := os.Stdout
+	t.Cleanup(func() {
+		os.Stdout = stdout
+	})
+	os.Stdout = nil
+	verbose.Set(true)
+	verbose.Printf("")
+	verbose.Println()
+}
+
+func testPrintfPrintln(t *testing.T, v bool) {
+	t.Run("start verbose printer with verbose "+strconv.FormatBool(v), func(t *testing.T) {
+		stdout, stderr := new(strings.Builder), new(strings.Builder)
+		stdout.Grow(len(wantStdout))
+		cmd := exec.Command(os.Args[0], "-test.run=TestPrinter")
+		cmd.Stdout, cmd.Stderr = stdout, stderr
+		if v {
+			cmd.Env = append(cmd.Env, testVerbose+"=1")
+		} else {
+			cmd.Env = append(cmd.Env, testVerbose+"=0")
+		}
+		if err := cmd.Run(); err != nil {
+			panic("cannot run printer process: " + err.Error() + " stderr: " + stderr.String())
+		}
+
+		if got := stdout.String(); strings.Contains(got, wantStdout) != v {
+			t.Errorf("Print: got %v; want %t",
+				got, v)
+		}
+	})
+}
diff --git a/internal/verbose/state_test.go b/internal/verbose/state_test.go
new file mode 100644
index 0000000..21a03be
--- /dev/null
+++ b/internal/verbose/state_test.go
@@ -0,0 +1,20 @@
+package verbose_test
+
+import (
+	"testing"
+
+	"git.ophivana.moe/cat/fortify/internal/verbose"
+)
+
+func TestGetSet(t *testing.T) {
+	verbose.Set(false)
+	if verbose.Get() {
+		t.Errorf("Get() = true, want false")
+	}
+
+	verbose.Set(true)
+	if !verbose.Get() {
+		t.Errorf("Get() = false, want true")
+	}
+
+}