diff --git a/pyqso/auxiliary_dialogs.py b/pyqso/auxiliary_dialogs.py
index 06e8bc0..bb0b73b 100644
--- a/pyqso/auxiliary_dialogs.py
+++ b/pyqso/auxiliary_dialogs.py
@@ -28,7 +28,7 @@ def error(parent, message):
     :arg str message: The message to display to the user.
     """
     logging.error(message)
-    _handle_gtk_dialog(parent, Gtk.MessageType.ERROR, message, "Error")
+    handle_gtk_dialog(parent, Gtk.MessageType.ERROR, message, "Error")
 
 
 def info(parent, message):
@@ -38,7 +38,7 @@ def info(parent, message):
     :arg str message: The message to display to the user.
     """
     logging.debug(message)
-    _handle_gtk_dialog(parent, Gtk.MessageType.INFO, message, "Information")
+    handle_gtk_dialog(parent, Gtk.MessageType.INFO, message, "Information")
 
 
 def question(parent, message):
@@ -49,10 +49,10 @@ def question(parent, message):
     :returns: The 'yes'/'no' response from the user.
     :rtype: Gtk.ResponseType
     """
-    return _handle_gtk_dialog(parent, Gtk.MessageType.QUESTION, message, "Question")
+    return handle_gtk_dialog(parent, Gtk.MessageType.QUESTION, message, "Question")
 
 
-def _handle_gtk_dialog(parent, msgtype, message, title):
+def handle_gtk_dialog(parent, msgtype, message, title):
     """
     Instantiate and present a dialog to the user.
 
diff --git a/pyqso/logbook.py b/pyqso/logbook.py
index 14408a4..ceda309 100644
--- a/pyqso/logbook.py
+++ b/pyqso/logbook.py
@@ -58,7 +58,11 @@ class Logbook:
         return
 
     def new(self, widget=None):
-        """ Create a new logbook, and open it. """
+        """ Create a new logbook, and open it.
+
+        :returns: True if the new logbook is successfully opened, and False otherwise.
+        :rtype: bool
+        """
 
         # Get the new file's path from a dialog.
         dialog = Gtk.FileChooserDialog("Create a New SQLite Database File",
@@ -82,13 +86,16 @@ class Logbook:
             # Clear the contents of the file, in case the file exists already.
             open(path, 'w').close()
             # Open the new logbook, ready for use.
-            self.open(path=path)
-        return
+            opened = self.open(path=path)
+        return opened
 
-    def open(self, widget=None, path=None):
+    def open(self, widget=None, path=None, render=True):
         """ Open a logbook, and render all the logs within it.
 
         :arg str path: An optional argument containing the database file location, if already known. If this is None, a file selection dialog will appear.
+        :arg bool render: An optional argument to specify whether or not the logs should be rendered in the logbook. By default this is True, but is sometimes set to False for unit testing purposes.
+        :returns: True if the logbook is successfully opened, and False otherwise.
+        :rtype: bool
         """
 
         if(path is None):
@@ -106,7 +113,7 @@ class Logbook:
 
             if(path is None):  # If the Cancel button has been clicked, path will still be None
                 logging.debug("No file path specified.")
-                return
+                return False
 
         connected = self.db_connect(path)
         if(connected):
@@ -118,46 +125,52 @@ class Logbook:
             self.logs = self.get_logs()
             if(self.logs is None):
                 error(parent=self.application.window, message="Could not open logbook. Something went wrong when trying to retrieve the logs. Perhaps the logbook file is encrypted, corrupted, or in the wrong format?")
-                return
+                return False
             else:
                 logging.debug("All logs retrieved successfully.")
 
-            logging.debug("Rendering logs...")
-            # For rendering the logs. One treeview and one treeselection per Log.
-            self.treeview = []
-            self.treeselection = []
-            self.sorter = []
-            self.filter = []
-            self.summary = Summary(self.application)
-            self.blank = Blank(self.application)
+            if(render):
+                logging.debug("Rendering logs...")
+                # For rendering the logs. One treeview and one treeselection per Log.
+                self.treeview = []
+                self.treeselection = []
+                self.sorter = []
+                self.filter = []
+                self.summary = Summary(self.application)
+                self.blank = Blank(self.application)
 
-            # FIXME: This is an unfortunate work-around. If the area around the "+/New Log" button
-            # is clicked, PyQSO will change to an empty page. This signal is used to stop this from happening.
-            self.notebook.connect("switch-page", self.on_switch_page)
+                # FIXME: This is an unfortunate work-around. If the area around the "+/New Log" button
+                # is clicked, PyQSO will change to an empty page. This signal is used to stop this from happening.
+                self.notebook.connect("switch-page", self.on_switch_page)
 
-            for i in range(len(self.logs)):
-                self.render_log(i)
-            logging.debug("All logs rendered successfully.")
+                for i in range(len(self.logs)):
+                    self.render_log(i)
+                logging.debug("All logs rendered successfully.")
 
-            self.summary.update()
-            self.application.toolbox.awards.count(self)
+                self.summary.update()
+                self.application.toolbox.awards.count(self)
 
-            context_id = self.application.statusbar.get_context_id("Status")
-            self.application.statusbar.push(context_id, "Logbook: %s" % self.path)
-            self.application.toolbar.set_logbook_button_sensitive(False)
-            self.application.menu.set_logbook_item_sensitive(False)
-            self.application.menu.set_log_items_sensitive(True)
-            self.application.toolbar.filter_source.set_sensitive(True)
+                context_id = self.application.statusbar.get_context_id("Status")
+                self.application.statusbar.push(context_id, "Logbook: %s" % self.path)
+                self.application.toolbar.set_logbook_button_sensitive(False)
+                self.application.menu.set_logbook_item_sensitive(False)
+                self.application.menu.set_log_items_sensitive(True)
+                self.application.toolbar.filter_source.set_sensitive(True)
 
-            self.notebook.show_all()
+                self.notebook.show_all()
 
         else:
             logging.debug("Not connected to a logbook. No logs were opened.")
+            return False
 
-        return
+        return True
 
     def close(self, widget=None):
-        """ Close the logbook that is currently open. """
+        """ Close the logbook that is currently open.
+
+        :returns: True if the logbook is successfully closed, and False otherwise.
+        :rtype: bool
+        """
 
         disconnected = self.db_disconnect()
         if(disconnected):
@@ -176,7 +189,9 @@ class Logbook:
             self.application.toolbar.filter_source.set_sensitive(False)
         else:
             logging.debug("Unable to disconnect from the database. No logs were closed.")
-        return
+            return False
+
+        return True
 
     def db_connect(self, path):
         """ Create an SQL database connection to the Logbook's data source.
diff --git a/tests/test_logbook.py b/tests/test_logbook.py
index d22ac76..1cca54b 100644
--- a/tests/test_logbook.py
+++ b/tests/test_logbook.py
@@ -32,25 +32,36 @@ class TestLogbook(unittest.TestCase):
 
     def setUp(self):
         """ Set up the Logbook object and connection to the test database needed for the unit tests. """
+
         self.logbook = Logbook(application=mock.MagicMock())
+
+        # Open the test database file.
         path_to_test_database = os.path.join(os.path.realpath(os.path.dirname(__file__)), os.pardir, "res/test.db")
-        success = self.logbook.db_connect(path_to_test_database)
-        assert(success)
-        self.logbook.logs = self.logbook.get_logs()
-        assert(self.logbook.logs is not None)
+        opened = self.logbook.open(path=path_to_test_database, render=False)
+        assert(opened)
+        assert(self.logbook.connection is not None)
+
         # Check that the logs have been retrieved.
-        temp = []
-        for log_name in ["test", "test2"]:
-            l = Log(self.logbook.connection, log_name)
-            l.populate()
-            temp.append(l)
-        assert(self.logbook.logs[0].name == temp[0].name)
-        assert(self.logbook.logs[1].name == temp[1].name)
+        assert(len(self.logbook.logs) == 2)
+        assert(self.logbook.logs[0].name == "test")
+        assert(self.logbook.logs[1].name == "test2")
 
     def tearDown(self):
         """ Disconnect from the test database. """
-        success = self.logbook.db_disconnect()
-        assert(success)
+        self.logbook.notebook.get_n_pages.return_value = 0
+        closed = self.logbook.close()
+        assert(closed)
+
+    @mock.patch('pyqso.auxiliary_dialogs.handle_gtk_dialog')
+    def test_open_invalid_log(self, mock_handle_gtk_dialog):
+        """ Open an invalid database file and check that an error occurs. """
+        path_to_invalid_database = "Logbook.test_setUp_invalid.txt"
+        f = open("Logbook.test_setUp_invalid.txt", 'w')
+        f.write("This is a plain text file. Trying to open this file in PyQSO should case an error, since it is not a valid database file.")
+        f.close()
+        opened = self.logbook.open(path=path_to_invalid_database, render=False)
+        assert(not opened)
+        assert(self.logbook.logs is None)
 
     def test_log_name_exists(self):
         """ Check that only the log called 'test' exists. """
diff --git a/tests/test_record_dialog.py b/tests/test_record_dialog.py
index 162e5fe..ec9ffe7 100644
--- a/tests/test_record_dialog.py
+++ b/tests/test_record_dialog.py
@@ -57,7 +57,7 @@ class TestRecordDialog(unittest.TestCase):
     def test_convert_frequency(self):
         """ Check that a frequency can be successfully converted from one unit to another. """
         frequency = "7.140"  # In MHz
-        converted = self.record_dialog.convert_frequency(frequency, from_unit="MHz", to_unit="AHz")  # Unknown to_unit. This should return the input unmodified.
+        converted = self.record_dialog.convert_frequency(frequency, from_unit="MHz", to_unit="AHz")  # Unknown to_unit. This should return the input unmodified (and give an error message).
         assert(converted == frequency)
         converted = self.record_dialog.convert_frequency(frequency, from_unit="MHz", to_unit="kHz")  # Convert from MHz to kHz.
         assert(float(converted) == 1e3*float(frequency))