simplified existing test, added a new test

tests/Composer/Test/Fixtures/installer/github-issues-4795-2.test

@@ -0,0 +1,44 @@
+--TEST--
+
+See Github issue #4795 ( github.com/composer/composer/issues/4795 ).
+
+Composer\Installer::whitelistUpdateDependencies should not output a warning for dependencies that need to be updated
+that are also a root package, when that root package is also explicitly whitelisted.
+
+--COMPOSER--
+{
+    "repositories": [
+        {
+            "type": "package",
+            "package": [
+                { "name": "a", "version": "1.0.0" },
+                { "name": "a", "version": "1.1.0" },
+                { "name": "b", "version": "1.0.0", "require": { "a": "~1.0" } },
+                { "name": "b", "version": "1.1.0", "require": { "a": "~1.1" } }
+            ]
+        }
+    ],
+    "require": {
+        "a": "~1.0",
+        "b": "~1.0"
+    }
+}
+
+--INSTALLED--
+[
+    { "name": "a", "version": "1.0.0" },
+    { "name": "b", "version": "1.0.0", "require": { "a": "~1.0" } }
+]
+
+--RUN--
+update a b --with-dependencies
+
+--EXPECT-OUTPUT--
+Loading composer repositories with package information
+Updating dependencies (including require-dev)
+Writing lock file
+Generating autoload files
+
+--EXPECT--
+Updating a (1.0.0) to a (1.1.0)
+Updating b (1.0.0) to b (1.1.0)

tests/Composer/Test/Fixtures/installer/github-issues-4795.test

@@ -14,27 +14,24 @@ dependency of one the requirements that is whitelisted for update.
                 { "name": "a", "version": "1.0.0" },
                 { "name": "a", "version": "1.1.0" },
                 { "name": "b", "version": "1.0.0", "require": { "a": "~1.0" } },
-                { "name": "b", "version": "1.1.0", "require": { "a": "~1.1" } },
-                { "name": "c", "version": "1.0.0", "require": { "a": "~1.0" } }
+                { "name": "b", "version": "1.1.0", "require": { "a": "~1.1" } }
             ]
         }
     ],
     "require": {
         "a": "~1.0",
-        "b": "~1.0",
-        "c": "~1.0"
+        "b": "~1.0"
     }
 }
 
 --INSTALLED--
 [
     { "name": "a", "version": "1.0.0" },
-    { "name": "b", "version": "1.0.0", "require": { "a": "~1.0" } },
-    { "name": "c", "version": "1.0.0", "require": { "a": "~1.0" } }
+    { "name": "b", "version": "1.0.0", "require": { "a": "~1.0" } }
 ]
 
 --RUN--
-update B --with-dependencies
+update b --with-dependencies
 
 --EXPECT-OUTPUT--
 <warning>Dependency "a" is also a root requirement, but is not explicitly whitelisted. Ignoring.</warning>