Fixing test command to use vendored modules
Added first unit test

Change-Id: I88f6ca906764dbb9a071607bc0e9410d1b84ef0c
diff --git a/internal/bbsim/devices/helpers_test.go b/internal/bbsim/devices/helpers_test.go
new file mode 100644
index 0000000..2d01c1a
--- /dev/null
+++ b/internal/bbsim/devices/helpers_test.go
@@ -0,0 +1,84 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package devices
+
+import (
+	"github.com/looplab/fsm"
+	"gotest.tools/assert"
+	"testing"
+)
+
+var (
+	originalNewFSM func(initial string, events []fsm.EventDesc, callbacks map[string]fsm.Callback) *fsm.FSM
+)
+
+func setUp(t *testing.T)  {
+	originalNewFSM = newFSM
+}
+
+
+func tearDown()  {
+	newFSM = originalNewFSM
+}
+
+func Test_Helpers(t *testing.T) {
+
+	// feedback values for the mock
+	called := 0
+	args := struct {
+		initial string
+		events []fsm.EventDesc
+		callbacks map[string]fsm.Callback
+	}{}
+
+	// creating the mock function
+	mockFSM := func(initial string, events []fsm.EventDesc, callbacks map[string]fsm.Callback) *fsm.FSM  {
+		called++
+		args.initial = initial
+		args.events = events
+		args.callbacks = callbacks
+		return fsm.NewFSM(initial, events, callbacks)
+	}
+	newFSM = mockFSM
+
+	// params for the method under test
+	cb_called := 0
+	cb := func(e *fsm.Event) {
+		cb_called++
+		return
+	}
+
+	// calling the method under test
+	sm := getOperStateFSM(cb)
+
+	// verify
+	assert.Equal(t, called, 1, "Expected fsm.NewFSM to have been called once, instead it was called %d", called)
+	assert.Equal(t, args.initial, "down")
+
+	assert.Equal(t, args.events[0].Name, "enable")
+	assert.Equal(t, args.events[0].Src[0], "down")
+	assert.Equal(t, args.events[0].Dst, "up")
+
+	assert.Equal(t, args.events[1].Name, "disable")
+	assert.Equal(t, args.events[1].Src[0], "up")
+	assert.Equal(t, args.events[1].Dst, "down")
+
+	// this is to test that the callback is called when the state change
+	sm.Event("enable")
+	assert.Equal(t, cb_called, 1)
+
+}
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