Issue 26167. Test for indexing a unit which is not attached to a library.

pkg/analysis_server/test/services/index/index_test.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/summary/idl.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
+import 'package:typed_mock/typed_mock.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../abstract_single_unit.dart';
 import '../../utils.dart';
 
 main() {
   initializeTestEnvironment();
   defineReflectiveTests(IndexTest);
 }
 
@@ skipping 229 matching lines @@
   test_indexDeclarations_nullUnit() async {
     index.indexDeclarations(null);
   }
 
   test_indexDeclarations_nullUnitElement() async {
     resolveTestUnit('');
     testUnit.element = null;
     index.indexDeclarations(testUnit);
   }
 
+  test_indexUnit_nullLibraryElement() async {
+    resolveTestUnit('');
+    CompilationUnitElement unitElement = new _CompilationUnitElementMock();
+    expect(unitElement.library, isNull);
+    testUnit.element = unitElement;
+    index.indexUnit(testUnit);
+  }
+
   test_indexUnit_nullUnit() async {
     index.indexUnit(null);
   }
 
   test_indexUnit_nullUnitElement() async {
     resolveTestUnit('');
     testUnit.element = null;
     index.indexUnit(testUnit);
   }
 
@@ skipping 64 matching lines @@
     }
   }
 
   Source _indexUnit(String path, String code) {
     Source source = addSource(path, code);
     CompilationUnit unit = resolveLibraryUnit(source);
     index.indexUnit(unit);
     return source;
   }
 }
+
+class _CompilationUnitElementMock extends TypedMock
+    implements CompilationUnitElement {}