Python: supress non-useful results (w/ tests) for iter str/seq query

Fixes github#3207

Author: RasmusWL

python/ql/src/Statements/IterableStringOrSequence.ql

@@ -12,6 +12,7 @@
  */
 
 import python
+import semmle.python.filters.Tests
 
 predicate has_string_type(Value v) {
     v.getClass() = ClassValue::str()
@@ -28,7 +29,10 @@ where
     iter.pointsTo(seq, seq_origin) and
     has_string_type(str) and
     seq.getClass().isIterable() and
-    not has_string_type(seq)
+    not has_string_type(seq) and
+    // suppress occurrences from tests
+    not seq_origin.getScope().getScope*() instanceof TestScope and
+    not str_origin.getScope().getScope*() instanceof TestScope
 select loop,
     "Iteration over $@, of class " + seq.getClass().getName() + ", may also iterate over $@.",
     seq_origin, "sequence", str_origin, "string"

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

@@ -1,3 +1 @@
 | 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 |