diff --git a/logger_test.go b/logger_test.go
new file mode 100644
index 0000000..5651d6d
--- /dev/null
+++ b/logger_test.go
@@ -0,0 +1,71 @@
+/**
+ * This file is part of tz.
+ *
+ * tz is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free
+ * Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * tz is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with tz.  If not, see <https://www.gnu.org/licenses/>.
+ **/
+package main
+
+import (
+	"fmt"
+	"os"
+	"math/rand"
+	"strings"
+	"testing"
+)
+
+func TestLogger(t *testing.T) {
+	oldDebug := os.Getenv("DEBUG")
+	os.Setenv("DEBUG", "1")
+	SetupLogger()
+
+	logMsg := fmt.Sprintf("Hello world %v!", rand.Int())
+	logger.Printf(logMsg)
+
+	out, err := os.ReadFile("debug.log")
+	if err != nil {
+		t.Errorf("Could not read log file debug.log: %v", err)
+	}
+	lines := strings.Split(string(out), "\n")
+	lastLine := lines[len(lines) - 2] // ignore trailing newline
+	if !strings.Contains(lastLine, logMsg) {
+		t.Errorf("Missing log line in debug.log: %s", logMsg)
+	}
+
+	if oldDebug != "1" {
+		os.Setenv("DEBUG", oldDebug)
+		SetupLogger()
+	}
+}
+
+func TestNoLogger(t *testing.T) {
+	oldDebug, debugWasSet := os.LookupEnv("DEBUG")
+	os.Unsetenv("DEBUG")
+	SetupLogger()
+
+	logMsg := fmt.Sprintf("Not logged %v!", rand.Int())
+	logger.Print(logMsg)
+
+	out, err := os.ReadFile("debug.log")
+	if err != nil {
+		t.Errorf("Could not read log file debug.log: %v", err)
+	}
+	if strings.Contains(string(out), logMsg) {
+		t.Errorf("Log file debug.log contained forbidden string: %s", logMsg)
+	}
+
+	if debugWasSet {
+		os.Setenv("DEBUG", oldDebug)
+		SetupLogger()
+	}
+}