Mock KVStore for Mattermost plugin unit testing

mock_kv_store.go

package main

import (
	"github.com/mattermost/mattermost/server/public/plugin/plugintest"
	"github.com/stretchr/testify/mock"
)

type testKVStore map[string][]byte

func makeTestKVStore(api *plugintest.API, initialValues testKVStore) testKVStore {
	testStore := initialValues
	if testStore == nil {
		testStore = testKVStore{}
	}

	kvCall := api.On("KVGet", mock.Anything).Maybe().Return(nil, nil)
	kvCall.Run(func(args mock.Arguments) {
		key := args.Get(0).(string)
		val, ok := testStore[key]
		if ok {
			kvCall.Return(val, nil)
		} else {
			kvCall.Return(nil, nil)
		}
	})

	api.On("KVSet", mock.Anything, mock.Anything).Maybe().Return(nil).Run(func(args mock.Arguments) {
		key := args.Get(0).(string)
		value := args.Get(1).([]byte)
		testStore[key] = value
	})

	return testStore
}

x_kv_scratch.go

package main

func (p *Plugin) KVScratch() {
	p.API.KVSet("mykey", []byte("my value"))

	initialValue, _ := p.API.KVGet("initial")
	p.API.KVSet("fetched", initialValue)
}

x_kv_scratch_test.go

package main

import (
	"testing"

	"github.com/mattermost/mattermost/server/public/plugin/plugintest"
	"github.com/stretchr/testify/require"
)

func TestKVScratch(t *testing.T) {
	p := &Plugin{}
	api := &plugintest.API{}
	p.SetAPI(api)

	testStore := makeTestKVStore(api, testKVStore{
		"initial": []byte("initial value"),
	})

	p.KVScratch()

	require.Equal(t, "my value", string(testStore["mykey"]))
	require.Equal(t, "initial value", string(testStore["fetched"]))
}