C#: Fix bad join order in TestLibrary characteristic predicate.

Author: michaelnebel

csharp/ql/src/Telemetry/ExternalApi.qll

@@ -11,17 +11,19 @@ private import semmle.code.csharp.dataflow.internal.DataFlowDispatch as DataFlow
 private import semmle.code.csharp.dataflow.internal.TaintTrackingPrivate
 private import semmle.code.csharp.security.dataflow.flowsources.Remote
 
+pragma[nomagic]
+private predicate isTestNamespace(Namespace ns) {
+  ns.getFullName()
+      .matches([
+          "NUnit.Framework%", "Xunit%", "Microsoft.VisualStudio.TestTools.UnitTesting%", "Moq%"
+        ])
+}
+
 /**
  * A test library.
  */
 class TestLibrary extends RefType {
-  TestLibrary() {
-    this.getNamespace()
-        .getFullName()
-        .matches([
-            "NUnit.Framework%", "Xunit%", "Microsoft.VisualStudio.TestTools.UnitTesting%", "Moq%"
-          ])
-  }
+  TestLibrary() { isTestNamespace(this.getNamespace()) }
 }
 
 /** Holds if the given callable is not worth supporting. */