Add tests for DependencyGraph (postcss#354)

* Make depGraph testable

* Add tests for DependencyGraph

Author: RyanZim

index.js

@@ -15,8 +15,9 @@ const postcssrc = require('postcss-load-config')
 const reporter = require('postcss-reporter/lib/formatter')()
 
 const argv = require('./lib/args')
-const depGraph = require('./lib/depGraph')
+const createDependencyGraph = require('./lib/DependencyGraph')
 const getMapfile = require('./lib/getMapfile')
+const depGraph = createDependencyGraph()
 
 let input = argv._
 const { dir, output } = argv

lib/DependencyGraph.js

@@ -0,0 +1,24 @@
+'use strict'
+const path = require('path')
+const { DepGraph } = require('dependency-graph')
+
+module.exports = function () {
+  const graph = new DepGraph()
+  return {
+    add(message) {
+      message.parent = path.resolve(message.parent)
+      message.file = path.resolve(message.file)
+
+      graph.addNode(message.parent)
+      graph.addNode(message.file)
+      graph.addDependency(message.parent, message.file)
+      return message
+    },
+    dependantsOf(node) {
+      node = path.resolve(node)
+
+      if (graph.hasNode(node)) return graph.dependantsOf(node)
+      return []
+    },
+  }
+}

lib/DependencyGraph.test.js

@@ -0,0 +1,20 @@
+'use strict'
+const test = require('ava')
+const path = require('path')
+const createDependencyGraph = require('./DependencyGraph.js')
+
+function resolveArray(arr) {
+  return arr.map((p) => path.resolve(p))
+}
+
+test('tracks dependencies', (t) => {
+  const graph = createDependencyGraph()
+  graph.add({ file: 'aa', parent: 'a' })
+  graph.add({ file: 'bb', parent: 'b' })
+  graph.add({ file: 'ab', parent: 'a' })
+  graph.add({ file: 'ab', parent: 'b' })
+  t.deepEqual(graph.dependantsOf('aa'), resolveArray(['a']))
+  t.deepEqual(graph.dependantsOf('bb'), resolveArray(['b']))
+  t.deepEqual(graph.dependantsOf('ab'), resolveArray(['a', 'b']))
+  t.deepEqual(graph.dependantsOf('nonexistent'), [])
+})

lib/depGraph.js

@@ -48,7 +48,8 @@
   "files": [
     "bin",
     "index.js",
-    "lib"
+    "lib",
+    "!*.test.js"
   ],
   "keywords": [
     "cli",