Clean up tests that are duplicated between install and update.

sdk/lib/_internal/pub/test/hosted/remove_removed_dependency_test.dart

+// Copyright (c) 2012, 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.
+
+library pub_tests;
+
+import 'dart:io';
+
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+
+main() {
+  initConfig();
+
+  forBothPubInstallAndUpdate((command) {
+    integration("removes a dependency that's removed from the pubspec", () {
+      servePackages([
+        packageMap("foo", "1.0.0"),
+        packageMap("bar", "1.0.0")
+      ]);
+
+      d.appDir([dependencyMap("foo"), dependencyMap("bar")]).create();
+
+      pubCommand(command);
+
+      d.packagesDir({
+        "foo": "1.0.0",
+        "bar": "1.0.0"
+      }).validate();
+
+      d.appDir([dependencyMap("foo")]).create();
+
+      pubCommand(command);
+
+      d.packagesDir({
+        "foo": "1.0.0",
+        "bar": null
+      }).validate();
+    });
+  });
+}