Make flat-module-tree spec more accurate

test/spec/flat-module-tree/package.json

@@ -1,5 +1,7 @@
 {
-	"dependencies": {
-	    "nested":"*"
-	}
-}
+	"_args": [],
+    "dependencies": {
+        "http-server": "1",
+        "url": "2"
+    }
+}

test/spec/flat-module-tree/program.js

@@ -1,4 +1,44 @@
+/*
+ * Up to npm 3, npm always installed packages in the package's node_modules
+ * directory. Starting in npm 3, npm now tries to avoid duplication by floating
+ * dependencies-of-dependencies as far up the directory structure as possible
+ * without causing version conflicts.
+ *
+ * This means when a module requires a node_module, that dependency may have
+ * been installed to ./node_modules, ../node_modules, ../../node_modules, etc.
+ * There is no way to determine where a dependency has been installed (until
+ * npm 5's package-lock.json), as npm 3+ is non-deterministic and the location
+ * a dependency is installed to can change depending on install order.
+ *
+ * Imagine a simple web application project that runs an http server. The
+ * packages are: http-server, url, and path. The dependencies between packages
+ * are:
+ *
+ * flat-module-tree -> [http-server@1, url@2]      flat-module-tree
+ * http-server@1 -> [path@1, url@1]                   /         \
+ * url@1 -> [path@1]                             http-server@1  url@2
+ * url@2 -> [path@2]                              /      \        |
+ * path@1 -> []                                path@1 <- url@1  path@2
+ * path@2 -> []
+ *
+ * This test's directory structure is a possible result of running npm install:
+ *
+ *           flat-module-tree
+ *                   |
+ *             node_modules
+ *             /     |    \
+ *  http-server@1  path@2  url@2
+ *        |
+ *   node_modules
+ *     /      \
+ *  url@1   path@1
+ *
+ * To understand how npm 3+ works and why it is non-deterministic, see
+ * https://npm.github.io/how-npm-works-docs/npm3/how-npm3-works.html
+ */
+
 var test = require('test');
-var nested = require('nested');
-test.assert(nested.foo() === 1, 'child module identifier');
+
+require("http-server");
+require("url");
 test.print('DONE', 'info');