Add unit tests for copy/paste support

pkg/analysis_server/test/src/computer/import_elements_computer_test.dart

+// Copyright (c) 2017, 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/protocol/protocol_generated.dart';
+import 'package:analysis_server/src/computer/import_elements_computer.dart';
+import 'package:analyzer/dart/analysis/results.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart';
+import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../../abstract_context.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(ImportElementsComputerTest);
+  });
+}
+
+/**
+ * Tests that the [ImportElementsComputer] will correctly update imports. The
+ * tests are generally labeled based on the kind of import in the source (from
+ * which the text was copied) and the kind of import in the target (into which
+ * the text was pasted). Kinds are a combination of "prefix", "hide", "show" and
+ * "deferred", or "bare" when there are none of the previous, or "none" when
+ * there is no import.
+ */
+@reflectiveTest
+class ImportElementsComputerTest extends AbstractContextTest {
+  String targetPath;
+  String targetCode;
+
+  ResolveResult result;
+
+  setUp() async {
+    super.setUp();
+    packageMap['p'] = [provider.newFolder(provider.convertPath('/p/lib'))];
+    targetPath = provider.convertPath('/p/lib/target.dart');
+    targetCode = '''
+main() {}
+''';
+    provider.newFile(targetPath, targetCode);
+    result = await driver.getResult(targetPath);
+  }
+
+  @failingTest
+  test_bare_none() {
+    List<ImportedElements> elements = <ImportedElements>[
+      new ImportedElements(provider.convertPath('/p/lib/a.dart'),
+          'package:p/a.dart', '', <String>['A']),
+    ];
+    List<SourceEdit> edits = _computeEditsFor(elements);
+    expect(edits, hasLength(1));
+    SourceEdit edit = edits[0];
+    expect(edit, isNotNull);
+    expect(edit.offset, 0);
+    expect(edit.length, 0);
+    expect(
+        edit.apply(targetCode),
+        """
+import 'source.dart';
+
+main() {}
+""");
+  }
+
+  test_none_none() {
+    List<ImportedElements> elements = <ImportedElements>[];
+    List<SourceEdit> edits = _computeEditsFor(elements);
+    expect(edits, hasLength(0));
+  }
+
+  List<SourceEdit> _computeEditsFor(List<ImportedElements> elements) {
+    ImportElementsComputer computer =
+        new ImportElementsComputer(result, targetPath, elements);
+    return computer.compute();
+  }
+}