Python: Fix (some) shortcomings of tests filter

python/ql/src/semmle/python/filters/Tests.qll

@@ -5,18 +5,17 @@ abstract class TestScope extends Scope { }
 // don't extend Class directly to avoid ambiguous method warnings
 class UnitTestClass extends TestScope {
     UnitTestClass() {
-        exists(ClassObject c | this = c.getPyClass() |
-            c.getASuperType() = theUnitTestPackage().attr(_)
+        exists(ClassValue cls | this = cls.getScope() |
+            cls.getABaseType+() = Module::named("unittest").attr(_)
             or
-            c.getASuperType().getName().toLowerCase() = "testcase"
+            cls.getABaseType+().getName().toLowerCase() = "testcase"
         )
     }
 }
 
-PackageObject theUnitTestPackage() { result.getName() = "unittest" }
-
 abstract class Test extends TestScope { }
 
+/** Class of test function that uses the `unittest` framework */
 class UnitTestFunction extends Test {
     UnitTestFunction() {
         this.getScope+() instanceof UnitTestClass and
@@ -37,3 +36,11 @@ class NoseTestFunction extends Test {
         this.(Function).getName().matches("test%")
     }
 }
+
+/** Class of functions that are clearly tests, but don't belong to a specific framework */
+class UnknownTestFunction extends Test {
+    UnknownTestFunction() {
+        this.(Function).getName().matches("test%") and
+        this.getEnclosingModule().getFile().getShortName().matches("test_%.py")
+    }
+}

python/ql/test/library-tests/filters/tests/Filter.expected

@@ -1,3 +1,6 @@
 | test.py:4:1:4:23 | Class MyTest |
 | test.py:6:5:6:21 | Function test_1 |
 | test.py:9:5:9:21 | Function test_2 |
+| test_foo.py:3:1:3:15 | Function test_foo |
+| unittest_test.py:3:1:3:33 | Class FooTest |
+| unittest_test.py:4:5:4:25 | Function test_valid |