Python: iter str/seq query gives non-useful results with tests

Author: RasmusWL

python/ql/test/3/query-tests/Statements/iter/IterableStringOrSequence.expected

@@ -1 +1,3 @@
 | statements_test.py:21:5:21:19 | For | Iteration over $@, of class list, may also iterate over $@. | statements_test.py:20:13:20:33 | ControlFlowNode for List | sequence | statements_test.py:18:13:18:26 | ControlFlowNode for Str | string |
+| supress_uses_from_tests.py:6:5:6:20 | For | Iteration over $@, of class list, may also iterate over $@. | supress_uses_from_tests.py:9:5:9:26 | ControlFlowNode for List | sequence | supress_uses_from_tests.py:19:17:19:27 | ControlFlowNode for Str | string |
+| supress_uses_from_tests.py:6:5:6:20 | For | Iteration over $@, of class list, may also iterate over $@. | supress_uses_from_tests.py:15:13:15:34 | ControlFlowNode for List | sequence | supress_uses_from_tests.py:19:17:19:27 | ControlFlowNode for Str | string |

python/ql/test/3/query-tests/Statements/iter/supress_uses_from_tests.py

@@ -0,0 +1,19 @@
+# This example illustrates that all valid results are not useful.
+# The alert in this file should be suppressed (TODO).
+# see https://github.com/Semmle/ql/issues/3207
+
+def foo(l):
+    for (k, v) in l:
+        print(k, v)
+
+foo([('a', 42), ('b', 43)])
+
+import unittest
+
+class FooTest(unittest.TestCase):
+    def test_valid(self):
+        foo([('a', 42), ('b', 43)])
+
+    def test_not_valid(self):
+        with six.assertRaises(self, ValueError):
+            foo("not valid")