fix: use Array#reduce and remove unneeded branch in prepGlobPatterns (#5

)

since arrify is called wherever this function is used.
Also add extra test case for which more accurately reflects a real project.

index.js

@@ -62,26 +62,13 @@ TestExclude.prototype.pkgConf = function (key, path) {
 }
 
 function prepGlobPatterns (patterns) {
-  if (!patterns) return patterns
-
-  const result = []
-
-  function add (pattern) {
-    if (result.indexOf(pattern) === -1) {
-      result.push(pattern)
-    }
-  }
-
-  patterns.forEach(function (pattern) {
+  return patterns.reduce(function (result, pattern) {
     // Allow gitignore style of directory exclusion
     if (!/\/\*\*$/.test(pattern)) {
-      add(pattern.replace(/\/$/, '') + '/**')
+      result = result.concat(pattern.replace(/\/$/, '') + '/**')
     }
-
-    add(pattern)
-  })
-
-  return result
+    return result.concat(pattern)
+  }, [])
 }
 
 module.exports = function (opts) {

test/fixtures/include-src-only/package.json

@@ -0,0 +1,7 @@
+{
+  "c": {
+    "include": [
+      "src/**/*.js"
+    ]
+  }
+}

test/test-exclude.js

@@ -50,6 +50,19 @@ describe('testExclude', function () {
       e.configFound.should.equal(true)
     })
 
+    it('should only instrument files that are included in subdirs', function () {
+      const e = exclude({
+        configPath: './test/fixtures/include-src-only',
+        configKey: 'c'
+      })
+      e.shouldInstrument('bar/baz.js').should.equal(false)
+      e.shouldInstrument('bad/file.js').should.equal(false)
+      e.shouldInstrument('foo.js').should.equal(false)
+
+      e.shouldInstrument('src/app.test.js').should.equal(false)
+      e.shouldInstrument('src/app.js').should.equal(true)
+    })
+
     it('should not throw if a key is missing', function () {
       var e = exclude({
         configPath: './test/fixtures/include',