resolves #765 resolve custom cache directory to an absolute path

index.js

@@ -49,7 +49,7 @@ function NYC (config) {
   this.cwd = config.cwd || process.cwd()
   this.reporter = arrify(config.reporter || 'text')
 
-  this.cacheDirectory = config.cacheDir || findCacheDir({name: 'nyc', cwd: this.cwd})
+  this.cacheDirectory = (config.cacheDir && path.resolve(config.cacheDir)) || findCacheDir({name: 'nyc', cwd: this.cwd})
   this.cache = Boolean(this.cacheDirectory && config.cache)
 
   this.exclude = testExclude({

test/nyc.js

@@ -1,6 +1,7 @@
 /* global describe, it */
 
 const NYC = require('../')
+const path = require('path')
 
 require('chai').should()
 
@@ -27,4 +28,21 @@ describe('NYC', function () {
       nyc._disableCachingTransform().should.equal(false)
     })
   })
+
+  describe('cacheDirectory', function () {
+    it('should resolve default cache folder to absolute path', function () {
+      const nyc = new NYC({
+        cache: true
+      })
+      path.isAbsolute(nyc.cacheDirectory).should.equal(true)
+    })
+
+    it('should resolve custom cache folder to absolute path', function () {
+      const nyc = new NYC({
+        cacheDir: '.nyc_cache',
+        cache: true
+      })
+      path.isAbsolute(nyc.cacheDirectory).should.equal(true)
+    })
+  })
 })