Move user_follow to separate file (#1210)

Also add unit tests

models/user_follow_test.go

@@ -0,0 +1,45 @@
+package models
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsFollowing(t *testing.T) {
+	assert.NoError(t, PrepareTestDatabase())
+	assert.True(t, IsFollowing(4, 2))
+	assert.False(t, IsFollowing(2, 4))
+	assert.False(t, IsFollowing(5, NonexistentID))
+	assert.False(t, IsFollowing(NonexistentID, 5))
+	assert.False(t, IsFollowing(NonexistentID, NonexistentID))
+}
+
+func TestFollowUser(t *testing.T) {
+	assert.NoError(t, PrepareTestDatabase())
+
+	testSuccess := func(followerID, followedID int64) {
+		assert.NoError(t, FollowUser(followerID, followedID))
+		AssertExistsAndLoadBean(t, &Follow{UserID: followerID, FollowID: followedID})
+	}
+	testSuccess(4, 2)
+	testSuccess(5, 2)
+
+	assert.NoError(t, FollowUser(2, 2))
+
+	CheckConsistencyFor(t, &User{})
+}
+
+func TestUnfollowUser(t *testing.T) {
+	assert.NoError(t, PrepareTestDatabase())
+
+	testSuccess := func(followerID, followedID int64) {
+		assert.NoError(t, UnfollowUser(followerID, followedID))
+		AssertNotExistsBean(t, &Follow{UserID: followerID, FollowID: followedID})
+	}
+	testSuccess(4, 2)
+	testSuccess(5, 2)
+	testSuccess(2, 2)
+
+	CheckConsistencyFor(t, &User{})
+}