C#: Add test cases for finding structurally equivalent control flow elements.

csharp/ql/test/library-tests/structuralcomparison/structuralComparison.ql

@@ -0,0 +1,24 @@
+import csharp
+import semmle.code.csharp.commons.StructuralComparison
+
+private class StructuralComparisonTest extends StructuralComparisonConfiguration {
+  StructuralComparisonTest() { this = "StructuralComparisonTest" }
+
+  /**
+   * All pairs of controls flow elements found in the source and within the same
+   * enclosing callable excluding all instances of `ThisAccess` to reduce the size
+   * of the output.
+   */
+  override predicate candidate(ControlFlowElement e1, ControlFlowElement e2) {
+    e1.fromSource() and
+    e2.fromSource() and
+    e1 != e2 and
+    e1.getEnclosingCallable() = e2.getEnclosingCallable() and
+    not e1 instanceof ThisAccess
+  }
+}
+
+query predicate same(ControlFlowElement e1, ControlFlowElement e2) {
+  exists(StructuralComparisonTest sct | sct.same(e1, e2))
+}
+// query predicate gvn(ControlFlowElement e, Gvn gvn) { gvn = toGvn(e) and e.fromSource() }