diff --git a/test/test_printers/test_printer_cups.py b/test/test_printers/test_printer_cups.py
index 96c3fda..cabc9cd 100644
--- a/test/test_printers/test_printer_cups.py
+++ b/test/test_printers/test_printer_cups.py
@@ -65,6 +65,7 @@ def test_open(cupsprinter, caplog, mocker):
     mocker.patch("escpos.printer.CupsPrinter.printers", new={"test_printer": "Test"})
 
     cupsprinter.printer_name = "test_printer"
+    assert cupsprinter.printer_name in cupsprinter.printers
 
     with caplog.at_level(logging.INFO):
         cupsprinter.open()
diff --git a/test/test_printers/test_printer_lp.py b/test/test_printers/test_printer_lp.py
index a84eb8c..440eec8 100644
--- a/test/test_printers/test_printer_lp.py
+++ b/test/test_printers/test_printer_lp.py
@@ -65,6 +65,7 @@ def test_open(lpprinter, caplog, mocker):
     mocker.patch("escpos.printer.LP.printers", new={"test_printer": "Test"})
 
     lpprinter.printer_name = "test_printer"
+    assert lpprinter.printer_name in lpprinter.printers
 
     with caplog.at_level(logging.INFO):
         lpprinter.open()
diff --git a/test/test_printers/test_printer_win32raw.py b/test/test_printers/test_printer_win32raw.py
index 52d8c71..cd33e0c 100644
--- a/test/test_printers/test_printer_win32raw.py
+++ b/test/test_printers/test_printer_win32raw.py
@@ -67,6 +67,10 @@ def test_open(win32rawprinter, caplog, mocker):
     THEN check the success is logged and the device property is set
     """
     mocker.patch("win32print.__init__")
+    mocker.patch("escpos.printer.Win32Raw.printers", new={"test_printer": "Test"})
+
+    win32rawprinter.printer_name = "test_printer"
+    assert win32rawprinter.printer_name in win32rawprinter.printers
 
     with caplog.at_level(logging.INFO):
         win32rawprinter.open()
@@ -83,6 +87,9 @@ def test_close_on_reopen(win32rawprinter, mocker):
     """
     mocker.patch("win32print.__init__")
     spy = mocker.spy(win32rawprinter, "close")
+    mocker.patch("escpos.printer.Win32Raw.printers", new={"test_printer": "Test"})
+
+    win32rawprinter.printer_name = "test_printer"
 
     win32rawprinter.open()
     assert win32rawprinter._device
@@ -98,6 +105,9 @@ def test_close(win32rawprinter, mocker, caplog):
     THEN check the closing is logged and the device property is False
     """
     mocker.patch("win32print.__init__")
+    mocker.patch("escpos.printer.Win32Raw.printers", new={"test_printer": "Test"})
+
+    win32rawprinter.printer_name = "test_printer"
 
     win32rawprinter.open()
     with caplog.at_level(logging.INFO):