fix(reporters): cannot read property map of undefined

Fixes #1662

lib/reporters/progress.js

@@ -4,6 +4,7 @@ var ProgressReporter = function (formatError, reportSlow, useColors, browserCons
   BaseReporter.call(this, formatError, reportSlow, useColors, browserConsoleLogOptions)
 
   this.EXCLUSIVELY_USE_COLORS = false
+  this._browsers = []
 
   this.writeCommonMsg = function (msg) {
     this.write(this._remove() + msg + this._render())

test/unit/reporters/progress.spec.js

@@ -0,0 +1,43 @@
+describe('reporter', function () {
+  var ProgressReporter = require('../../../lib/reporters/progress')
+
+  describe('Progress', function () {
+    var reporter
+    var formatError
+
+    beforeEach(function () {
+      formatError = sinon.spy()
+      reporter = new ProgressReporter(formatError, null, false, {terminal: true})
+    })
+
+    it('should turn off colors', function () {
+      expect(reporter.EXCLUSIVELY_USE_COLORS).to.equal(false)
+    })
+
+    it('should prepare state on run tests', function () {
+      sinon.stub(reporter, 'write')
+      sinon.stub(reporter, 'renderBrowser')
+
+      reporter.onRunStart()
+      reporter.onBrowserStart(createBrowserMock())
+
+      reporter.onRunStart()
+
+      expect(reporter._browsers.length).to.equal(0)
+      expect(reporter._isRendered).to.equal(false)
+    })
+
+    it('should not throw exception if browser exit with error without run tests', function () {
+      sinon.stub(reporter, 'write')
+      sinon.stub(reporter, 'renderBrowser')
+
+      expect(function () {
+        reporter.onBrowserError(createBrowserMock())
+      }).to.not.throw()
+    })
+
+    function createBrowserMock () {
+      return {}
+    }
+  })
+})