Python: add regression tests and organise tests

python/ql/test/experimental/dataflow/basic/maximalFlowsConfig.qll

@@ -0,0 +1,26 @@
+import experimental.dataflow.DataFlow
+
+/**
+ * A configuration to find all "maximal" flows.
+ * To be used on small programs.
+ */
+class MaximalFlowsConfig extends DataFlow::Configuration {
+  MaximalFlowsConfig() { this = "AllFlowsConfig" }
+
+  override predicate isSource(DataFlow::Node node) {
+    node instanceof DataFlow::ParameterNode
+    or
+    node = DataFlow::TEssaNode(_) and
+    not exists(DataFlow::Node pred |
+      pred = DataFlow::TEssaNode(_) and
+      DataFlow::localFlowStep(pred, node)
+    )
+  }
+
+  override predicate isSink(DataFlow::Node node) {
+    node instanceof DataFlow::ReturnNode
+    or
+    node = DataFlow::TEssaNode(_) and
+    not exists(node.asEssaNode().getASourceUse())
+  }
+}