Add integration tests for the execution domain.

pkg/analysis_server/test/integration/execution/delete_context_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/plugin/protocol/protocol.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../integration_tests.dart';
 
 main() {
   defineReflectiveSuite(() {
-    defineReflectiveTests(MapUriTest);
-    defineReflectiveTests(MapUriTest_Driver);
+    defineReflectiveTests(DeleteContextTest);
   });
 }
 
-class AbstractMapUriTest extends AbstractAnalysisServerIntegrationTest {
-  test_mapUri() async {
+@reflectiveTest
+class DeleteContextTest extends AbstractAnalysisServerIntegrationTest {
+  test_delete() async {
     String pathname = sourcePath('lib/main.dart');
     writeFile(pathname, '// dummy');
     writeFile(sourcePath('.packages'), 'foo:lib/');
     standardAnalysisSetup();
 
     String contextId =
-        (await sendExecutionCreateContext(sourceDirectory.path))?.id;
+        (await sendExecutionCreateContext(sourceDirectory.path)).id;
 
-    {
-      ExecutionMapUriResult result =
+    ExecutionMapUriResult result =
+        await sendExecutionMapUri(contextId, uri: 'package:foo/main.dart');
+    expect(result.file, pathname);
+
+    expect(await sendExecutionDeleteContext(contextId), isNull);
+
+    // After the delete, expect this to fail.
+    try {
+      result =
           await sendExecutionMapUri(contextId, uri: 'package:foo/main.dart');
-      expect(result.file, pathname);
-    }
+      fail('expected exception after context delete');
+    } catch (ignore) {}

[Paul Berry, 2017/02/12 14:39:04]

This won't work because the way the fail() method reports test failures is to
throw an exception, so the fact that you're catching *all* exceptions means that
even if MapUri doesn't report the expected error, the test will still pass.  We
don't want that.

See my comments in pkg/analysis_server/test/integration/integration_tests.dart. 
Assuming you take my advice there, this could change to:

} on ServerErrorMessage catch(message) {
  expect(message.error['code'], 'INVALID_PARAMETER');
}

[devoncarew, 2017/02/12 17:52:34]

Ah, good catch! I'll add a class as above.

+  }
 
-    {
-      ExecutionMapUriResult result =
-          await sendExecutionMapUri(contextId, file: pathname);
-      expect(result.uri, 'package:foo/main.dart');
-    }
-  }
-}
-
-@reflectiveTest
-class MapUriTest extends AbstractMapUriTest {}
-
-@reflectiveTest
-class MapUriTest_Driver extends AbstractMapUriTest {
   @override
   bool get enableNewAnalysisDriver => true;
 }