Address review: increase checkline() coverage

Author: Erlend E. Aasland

Lib/test/test_pdb.py

@@ -9,6 +9,7 @@
 import unittest
 import subprocess
 import textwrap
+import linecache
 
 from contextlib import ExitStack
 from io import StringIO
@@ -1295,6 +1296,9 @@ def test_pdb_issue_20766():
 
 
 class PdbTestCase(unittest.TestCase):
+    def setUp(self):
+        linecache.clearcache()  # Pdb.checkline() uses linecache.getline()
+
     def tearDown(self):
         os_helper.unlink(os_helper.TESTFN)
 
@@ -1806,14 +1810,34 @@ def test_issue42383(self):
             expected = '(Pdb) The correct file was executed'
             self.assertEqual(stdout.split('\n')[6].rstrip('\r'), expected)
 
-    def test_issue28528(self):
+    def test_checkline_before_debugging(self):
         with open(os_helper.TESTFN, "w") as f:
             f.write("print(123)")
         db = pdb.Pdb()
         self.assertEqual(db.checkline(os_helper.TESTFN, 1), 1)
+
+    def test_checkline_after_reset(self):
+        with open(os_helper.TESTFN, "w") as f:
+            f.write("print(123)")
+        db = pdb.Pdb()
         db.reset()
         self.assertEqual(db.checkline(os_helper.TESTFN, 1), 1)
 
+    def test_checkline_is_not_executable(self):
+        with open(os_helper.TESTFN, "w") as f:
+            # Test for comments, docstrings and empty lines
+            s = textwrap.dedent("""
+                # Comment
+                \"\"\" docstring \"\"\"
+                ''' docstring '''
+
+            """)
+            f.write(s)
+        db = pdb.Pdb()
+        num_lines = len(s.splitlines()) + 2  # Test for EOF
+        for lineno in range(num_lines):
+            self.assertFalse(db.checkline(os_helper.TESTFN, lineno))
+
 
 def load_tests(*args):
     from test import test_pdb