Add support for creating source ranges

pkg/analyzer_plugin/test/support/abstract_single_unit.dart

Index: pkg/analyzer_plugin/test/support/abstract_single_unit.dart
diff --git a/pkg/analyzer_plugin/test/support/abstract_single_unit.dart b/pkg/analyzer_plugin/test/support/abstract_single_unit.dart
new file mode 100644
index 0000000000000000000000000000000000000000..7faabe2470382c0b719e30a6da6bc3c526e6302a
--- /dev/null
+++ b/pkg/analyzer_plugin/test/support/abstract_single_unit.dart
@@ -0,0 +1,115 @@
+// 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 'dart:async';
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/error/error.dart';
+import 'package:analyzer/src/dart/ast/utilities.dart';
+import 'package:analyzer/src/dart/error/hint_codes.dart';
+import 'package:analyzer/src/generated/java_engine.dart';
+import 'package:analyzer/src/generated/source.dart';
+import 'package:test/test.dart';
+
+import 'abstract_context.dart';
+
+class AbstractSingleUnitTest extends AbstractContextTest {
+  bool verifyNoTestUnitErrors = true;
+
+  String testCode;
+  String testFile = '/test.dart';
+  Source testSource;
+  CompilationUnit testUnit;
+  CompilationUnitElement testUnitElement;
+  LibraryElement testLibraryElement;
+
+  void addTestSource(String code, [Uri uri]) {
+    testCode = code;
+    testSource = addSource(testFile, code, uri);
+  }
+
+  Element findElement(String name, [ElementKind kind]) {
+    return findChildElement(testUnitElement, name, kind);
+  }
+
+  int findEnd(String search) {
+    return findOffset(search) + search.length;
+  }
+
+  /**
+   * Returns the [SimpleIdentifier] at the given search pattern.
+   */
+  SimpleIdentifier findIdentifier(String search) {
+    return findNodeAtString(search, (node) => node is SimpleIdentifier);
+  }
+
+  AstNode findNodeAtOffset(int offset, [Predicate<AstNode> predicate]) {
+    AstNode result = new NodeLocator(offset).searchWithin(testUnit);
+    if (result != null && predicate != null) {
+      result = result.getAncestor(predicate);
+    }
+    return result;
+  }
+
+  AstNode findNodeAtString(String search, [Predicate<AstNode> predicate]) {
+    int offset = findOffset(search);
+    return findNodeAtOffset(offset, predicate);
+  }
+
+  Element findNodeElementAtString(String search,
+      [Predicate<AstNode> predicate]) {
+    AstNode node = findNodeAtString(search, predicate);
+    if (node == null) {
+      return null;
+    }
+    return ElementLocator.locate(node);
+  }
+
+  int findOffset(String search) {
+    int offset = testCode.indexOf(search);
+    expect(offset, isNonNegative, reason: "Not found '$search' in\n$testCode");
+    return offset;
+  }
+
+  int getLeadingIdentifierLength(String search) {
+    int length = 0;
+    while (length < search.length) {
+      int c = search.codeUnitAt(length);
+      if (c >= 'a'.codeUnitAt(0) && c <= 'z'.codeUnitAt(0)) {
+        length++;
+        continue;
+      }
+      if (c >= 'A'.codeUnitAt(0) && c <= 'Z'.codeUnitAt(0)) {
+        length++;
+        continue;
+      }
+      if (c >= '0'.codeUnitAt(0) && c <= '9'.codeUnitAt(0)) {
+        length++;
+        continue;
+      }
+      break;
+    }
+    return length;
+  }
+
+  Future<Null> resolveTestUnit(String code) async {
+    addTestSource(code);
+    var result = await driver.getResult(testFile);
+    testUnit = (result).unit;
+    if (verifyNoTestUnitErrors) {
+      expect(result.errors.where((AnalysisError error) {
+        return error.errorCode != HintCode.DEAD_CODE &&
+            error.errorCode != HintCode.UNUSED_CATCH_CLAUSE &&
+            error.errorCode != HintCode.UNUSED_CATCH_STACK &&
+            error.errorCode != HintCode.UNUSED_ELEMENT &&
+            error.errorCode != HintCode.UNUSED_FIELD &&
+            error.errorCode != HintCode.UNUSED_IMPORT &&
+            error.errorCode != HintCode.UNUSED_LOCAL_VARIABLE;
+      }), isEmpty);
+    }
+    testUnitElement = testUnit.element;
+    testLibraryElement = testUnitElement.library;
+  }
+}