Python: Add new-style tests

should perhaps move `LocalFlowStepTest` and `MaximalFlowStep` into where
 they are referenced (they did not seem too reusable after all).
Should also add argument tests in the same way.

Author: yoff

python/ql/test/experimental/dataflow/FlowTestUtil/FlowTest.qll

@@ -0,0 +1,31 @@
+import python
+import semmle.python.dataflow.new.DataFlow
+import TestUtilities.InlineExpectationsTest
+
+abstract class FlowTest extends InlineExpectationsTest {
+  bindingset[this]
+  FlowTest() { any() }
+
+  abstract string flowTag();
+
+  abstract predicate relevantFlow(DataFlow::Node fromNode, DataFlow::Node toNode);
+
+  override string getARelevantTag() { result = this.flowTag() }
+
+  override predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(DataFlow::Node fromNode, DataFlow::Node toNode | this.relevantFlow(fromNode, toNode) |
+      location = toNode.getLocation() and
+      tag = this.flowTag() and
+      value =
+        "\"" + fromNode.toString() + lineStr(fromNode, toNode) + " -> " + toNode.toString() + "\"" and
+      element = toNode.toString()
+    )
+  }
+
+  pragma[inline]
+  private string lineStr(DataFlow::Node fromNode, DataFlow::Node toNode) {
+    if fromNode.getLocation().getStartLine() = toNode.getLocation().getStartLine()
+    then result = ""
+    else result = ", l:" + fromNode.getLocation().getStartLine()
+  }
+}

python/ql/test/experimental/dataflow/FlowTestUtil/LocalFlowStepTest.qll

@@ -0,0 +1,13 @@
+import python
+import semmle.python.dataflow.new.DataFlow
+import FlowTest
+
+class LocalFlowStepTest extends FlowTest {
+  LocalFlowStepTest() { this = "LocalFlowStepTest" }
+
+  override string flowTag() { result = "step" }
+
+  override predicate relevantFlow(DataFlow::Node fromNode, DataFlow::Node toNode) {
+    DataFlow::localFlowStep(fromNode, toNode)
+  }
+}

python/ql/test/experimental/dataflow/FlowTestUtil/MaximalFlowTest.qll

@@ -0,0 +1,34 @@
+import python
+import semmle.python.dataflow.new.DataFlow
+import FlowTest
+
+class MaximalFlowTest extends FlowTest {
+  MaximalFlowTest() { this = "MaximalFlowTest" }
+
+  override string flowTag() { result = "flow" }
+
+  override predicate relevantFlow(DataFlow::Node source, DataFlow::Node sink) {
+    source != sink and
+    exists(MaximalFlowsConfig cfg | cfg.hasFlow(source, sink))
+  }
+}
+
+/**
+ * A configuration to find all "maximal" flows.
+ * To be used on small programs.
+ */
+class MaximalFlowsConfig extends DataFlow::Configuration {
+  MaximalFlowsConfig() { this = "MaximalFlowsConfig" }
+
+  override predicate isSource(DataFlow::Node node) {
+    not node.asCfgNode() instanceof CallNode and
+    not node.asCfgNode().getNode() instanceof Return and
+    not node instanceof DataFlow::ParameterNode and
+    not exists(DataFlow::Node pred | DataFlow::localFlowStep(pred, node))
+  }
+
+  override predicate isSink(DataFlow::Node node) {
+    not any(CallNode c).getArg(_) = node.asCfgNode() and
+    not exists(DataFlow::Node succ | DataFlow::localFlowStep(node, succ))
+  }
+}

python/ql/test/experimental/dataflow/basic/localFlowStepTest.expected

@@ -0,0 +1 @@
+import experimental.dataflow.FlowTestUtil.LocalFlowStepTest

python/ql/test/experimental/dataflow/basic/localFlowStepTest.ql

@@ -0,0 +1 @@
+import experimental.dataflow.FlowTestUtil.MaximalFlowTest

python/ql/test/experimental/dataflow/basic/maximalFlowTest.expected

@@ -1,7 +1,7 @@
-def obfuscated_id(x):
-  y = x
-  z = y
-  return z
+def obfuscated_id(x): #$ step="ControlFlowNode for FunctionExpr -> GSSA Variable obfuscated_id"
+  y = x #$ step="ControlFlowNode for x -> SSA variable y" step="SSA variable x, l:1 -> ControlFlowNode for x"
+  z = y #$ step="ControlFlowNode for y -> SSA variable z" step="SSA variable y, l:2 -> ControlFlowNode for y"
+  return z #$ flow="ControlFlowNode for IntegerLiteral, l:6 -> ControlFlowNode for z" step="SSA variable z, l:3 -> ControlFlowNode for z"
 
-a = 42
-b = obfuscated_id(a)
+a = 42 #$ step="ControlFlowNode for IntegerLiteral -> GSSA Variable a"
+b = obfuscated_id(a) #$ flow="ControlFlowNode for IntegerLiteral, l:6 -> GSSA Variable b" flow="ControlFlowNode for FunctionExpr, l:1 -> ControlFlowNode for obfuscated_id" step="ControlFlowNode for obfuscated_id() -> GSSA Variable b" step="GSSA Variable obfuscated_id, l:1 -> ControlFlowNode for obfuscated_id" step="GSSA Variable a, l:6 -> ControlFlowNode for a"

python/ql/test/experimental/dataflow/basic/maximalFlowTest.ql

@@ -0,0 +1,13 @@
+import python
+import experimental.dataflow.FlowTestUtil.FlowTest
+import experimental.dataflow.testConfig
+
+class DataFlowTest extends FlowTest {
+  DataFlowTest() { this = "DataFlowTest" }
+
+  override string flowTag() { result = "flow" }
+
+  override predicate relevantFlow(DataFlow::Node source, DataFlow::Node sink) {
+    exists(TestConfiguration cfg | cfg.hasFlow(source, sink))
+  }
+}