Use file_fixture to access test files in Rails 5

While writing tests sometimes we need to read files to compare the output. For example a test might want to compare the API response with pre determined data stored in a file.

Here is an example.

1
2# In test helper
3def file_data(name)
4  File.read(Rails.root.to_s + "/tests/support/files/#{name}")
5end
6
7# In test
8class PostsControllerTest < ActionDispatch::IntegrationTest
9  setup do
10    @post = posts(:one)
11  end
12
13  test "should get index" do
14    get posts_url, format: :json
15
16    assert_equal file_data('posts.json'), response.body
17  end
18end
19
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File Fixtures in Rails 5

In Rails 5, we can now organize such test files as fixtures.

Newly generated Rails 5 applications, will have directory test/fixtures/files to store such test files.

These test files can be accessed using file_fixture helper method in tests.

1require 'test_helper'
2
3class PostsControllerTest < ActionDispatch::IntegrationTest
4  setup do
5    @post = posts(:one)
6  end
7
8  test "should get index" do
9    get posts_url, format: :json
10
11    assert_equal response.body, file_fixture('posts.json').read
12  end
13end
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The file_fixture method returns Pathname object, so it's easy to extract file specific information.

1file_fixture('posts.json').read
2file_fixture('song.mp3').size
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