C++: Re-introduce most of the ast annotation test infrastructure

cpp/ql/test/TestUtilities/dataflow/FlowTestCommon.qll

@@ -13,6 +13,7 @@
 
 import cpp
 private import semmle.code.cpp.ir.dataflow.DataFlow::DataFlow as IRDataFlow
+private import semmle.code.cpp.dataflow.old.DataFlow::DataFlow as AstDataFlow
 import TestUtilities.InlineExpectationsTest
 
 class IRFlowTest extends InlineExpectationsTest {
@@ -40,3 +41,34 @@ class IRFlowTest extends InlineExpectationsTest {
     )
   }
 }
+
+class AstFlowTest extends InlineExpectationsTest {
+  AstFlowTest() { this = "ASTFlowTest" }
+
+  override string getARelevantTag() { result = "ast" }
+
+  override predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(
+      AstDataFlow::Node source, AstDataFlow::Node sink, AstDataFlow::Configuration conf, int n
+    |
+      tag = "ast" and
+      conf.hasFlow(source, sink) and
+      n = strictcount(AstDataFlow::Node otherSource | conf.hasFlow(otherSource, sink)) and
+      (
+        n = 1 and value = ""
+        or
+        // If there is more than one source for this sink
+        // we specify the source location explicitly.
+        n > 1 and
+        value =
+          source.getLocation().getStartLine().toString() + ":" +
+            source.getLocation().getStartColumn()
+      ) and
+      location = sink.getLocation() and
+      element = sink.toString()
+    )
+  }
+}
+
+/** DEPRECATED: Alias for AstFlowTest */
+deprecated class ASTFlowTest = AstFlowTest;