---
title: "Rails 5.1 introduced assert_changes and assert_no_changes"
description:
  "The BigBinary team's lesson on introduced assert_changes and
  assert_no_changes in Rails 5.1"
canonical_url: "https://www.bigbinary.com/blog/rails-5-1-introduced-assert_changes-and-assert_no_changes"
markdown_url: "https://www.bigbinary.com/blog/rails-5-1-introduced-assert_changes-and-assert_no_changes.md"
---

# Rails 5.1 introduced assert_changes and assert_no_changes

The BigBinary team's lesson on introduced assert_changes and assert_no_changes
in Rails 5.1

- Author: Narendra Rajput
- Published: May 9, 2017
- Categories: Rails 5.1, Rails

Rails 5.1 has introduced
[assert_changes](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_changes)
and
[assert_no_changes](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_no_changes).
It can be seen as a more generic version of
[assert_difference](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_difference)
and
[assert_no_difference](http://api.rubyonrails.org/classes/ActiveSupport/Testing/Assertions.html#method-i-assert_no_difference).

### assert_changes

`assert_changes` asserts the value of an expression is changed before and after
invoking the block. The specified expression can be string like
`assert_difference`.

```ruby

@user = users(:john)
assert_changes 'users(:john).status' do
  post :update, params: {id: @user.id, user: {status: 'online'}}
end

```

We can also pass a lambda as an expression.

```ruby

@user = users(:john)
assert_changes -> {users(:john).status} do
  post :update, params: {id: @user.id, user: {status: 'online'}}
end

```

`assert_changes` also allows options `:from` and `:to ` to specify initial and
final state of expression.

```ruby

@light = Light.new
assert_changes -> { @light.status }, from: 'off', to: 'on' do
  @light.turn_on
end

```

We can also specify test failure message.

```ruby

@invoice = invoices(:bb_client)
assert_changes -> { @invoice.status }, to: 'paid', 'Expected the invoice to be marked paid' do
  @invoice.make_payment
end

```

### assert_no_changes

`assert_no_changes` has same options and asserts that the expression doesn't
change before and after invoking the block.

## Links

- [Human page](https://www.bigbinary.com/blog/rails-5-1-introduced-assert_changes-and-assert_no_changes)