C#: Add a test that only prints 'base' flow summaries.

csharp/ql/test/library-tests/dataflow/library/FlowSummariesFiltered.ql

@@ -0,0 +1,21 @@
+import shared.FlowSummaries
+
+class IncludeFilteredSummarizedCallable extends IncludeSummarizedCallable {
+  IncludeFilteredSummarizedCallable() { this instanceof SummarizedCallable }
+
+  /**
+   * Holds if flow is propagated between `input` and `output` and
+   * if there is no summary for a callable in a `base` class or interface
+   * that propagates the same flow between `input` and `output`.
+   */
+  override predicate relevantSummary(
+    SummaryComponentStack input, SummaryComponentStack output, boolean preservesValue
+  ) {
+    this.propagatesFlow(input, output, preservesValue) and
+    not exists(IncludeSummarizedCallable rsc |
+      rsc.isAbstractOrInterface() and
+      this.(Virtualizable).overridesOrImplementsOrEquals(rsc) and
+      rsc.propagatesFlow(input, output, preservesValue)
+    )
+  }
+}