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A Guide to Testing Rails Applications
This guide covers built-in mechanisms in Rails for testing your application.
After reading this guide, you will know:
- Rails testing terminology.
- How to write unit, functional, and integration tests for your application.
- Other popular testing approaches and plugins.
Why Write Tests for your Rails Applications?
Rails makes it super easy to write your tests. It starts by producing skeleton test code while you are creating your models and controllers.
By simply running your Rails tests you can ensure your code adheres to the desired functionality even after some major code refactoring.
Rails tests can also simulate browser requests and thus you can test your application's response without having to test it through your browser.
Introduction to Testing
Testing support was woven into the Rails fabric from the beginning. It wasn't an "oh! let's bolt on support for running tests because they're new and cool" epiphany. Just about every Rails application interacts heavily with a database and, as a result, your tests will need a database to interact with as well. To write efficient tests, you'll need to understand how to set up this database and populate it with sample data.
The Test Environment
By default, every Rails application has three environments: development, test, and production. The database for each one of them is configured in config/database.yml
.
A dedicated test database allows you to set up and interact with test data in isolation. Tests can mangle test data with confidence, that won't touch the data in the development or production databases.
Rails Sets up for Testing from the Word Go
Rails creates a test
folder for you as soon as you create a Rails project using rails new
application_name. If you list the contents of this folder then you shall see:
$ ls -F test
controllers/ helpers/ mailers/ test_helper.rb
fixtures/ integration/ models/
The models
directory is meant to hold tests for your models, the controllers
directory is meant to hold tests for your controllers and the integration
directory is meant to hold tests that involve any number of controllers interacting.
Fixtures are a way of organizing test data; they reside in the fixtures
folder.
The test_helper.rb
file holds the default configuration for your tests.
The Low-Down on Fixtures
For good tests, you'll need to give some thought to setting up test data. In Rails, you can handle this by defining and customizing fixtures.
What Are Fixtures?
Fixtures is a fancy word for sample data. Fixtures allow you to populate your testing database with predefined data before your tests run. Fixtures are database independent written in YAML. There is one file per model.
You'll find fixtures under your test/fixtures
directory. When you run rails generate model
to create a new model fixture stubs will be automatically created and placed in this directory.
YAML
YAML-formatted fixtures are a very human-friendly way to describe your sample data. These types of fixtures have the .yml file extension (as in users.yml
).
Here's a sample YAML fixture file:
# lo & behold! I am a YAML comment!
david:
name: David Heinemeier Hansson
birthday: 1979-10-15
profession: Systems development
steve:
name: Steve Ross Kellock
birthday: 1974-09-27
profession: guy with keyboard
Each fixture is given a name followed by an indented list of colon-separated key/value pairs. Records are typically separated by a blank space. You can place comments in a fixture file by using the # character in the first column. Keys which resemble YAML keywords such as 'yes' and 'no' are quoted so that the YAML Parser correctly interprets them.
If you are working with associations, you can simply define a reference node between two different fixtures. Here's an example with a belongs_to/has_many association:
# In fixtures/categories.yml
about:
name: About
# In fixtures/articles.yml
one:
title: Welcome to Rails!
body: Hello world!
category: about
ERB'in It Up
ERB allows you to embed Ruby code within templates. The YAML fixture format is pre-processed with ERB when Rails loads fixtures. This allows you to use Ruby to help you generate some sample data. For example, the following code generates a thousand users:
<% 1000.times do |n| %>
user_<%= n %>:
username: <%= "user#{n}" %>
email: <%= "user#{n}@example.com" %>
<% end %>
Fixtures in Action
Rails by default automatically loads all fixtures from the test/fixtures
folder for your models and controllers test. Loading involves three steps:
- Remove any existing data from the table corresponding to the fixture
- Load the fixture data into the table
- Dump the fixture data into a variable in case you want to access it directly
Fixtures are Active Record objects
Fixtures are instances of Active Record. As mentioned in point #3 above, you can access the object directly because it is automatically setup as a local variable of the test case. For example:
# this will return the User object for the fixture named david
users(:david)
# this will return the property for david called id
users(:david).id
# one can also access methods available on the User class
email(david.girlfriend.email, david.location_tonight)
Unit Testing your Models
In Rails, models tests are what you write to test your models.
For this guide we will be using Rails scaffolding. It will create the model, a migration, controller and views for the new resource in a single operation. It will also create a full test suite following Rails best practices. We will be using examples from this generated code and will be supplementing it with additional examples where necessary.
NOTE: For more information on Rails scaffolding, refer to Getting Started with Rails
When you use rails generate scaffold
, for a resource among other things it creates a test stub in the test/models
folder:
$ bin/rails generate scaffold post title:string body:text
...
create app/models/post.rb
create test/models/post_test.rb
create test/fixtures/posts.yml
...
The default test stub in test/models/post_test.rb
looks like this:
require 'test_helper'
class PostTest < ActiveSupport::TestCase
# test "the truth" do
# assert true
# end
end
A line by line examination of this file will help get you oriented to Rails testing code and terminology.
require 'test_helper'
As you know by now, test_helper.rb
specifies the default configuration to run our tests. This is included with all the tests, so any methods added to this file are available to all your tests.
class PostTest < ActiveSupport::TestCase
The PostTest
class defines a test case because it inherits from ActiveSupport::TestCase
. PostTest
thus has all the methods available from ActiveSupport::TestCase
. You'll see those methods a little later in this guide.
Any method defined within a class inherited from MiniTest::Unit::TestCase
(which is the superclass of ActiveSupport::TestCase
) that begins with test
(case sensitive) is simply called a test. So, test_password
, test_valid_password
and testValidPassword
all are legal test names and are run automatically when the test case is run.
Rails adds a test
method that takes a test name and a block. It generates a normal MiniTest::Unit
test with method names prefixed with test_
. So,
test "the truth" do
assert true
end
acts as if you had written
def test_the_truth
assert true
end
only the test
macro allows a more readable test name. You can still use regular method definitions though.
NOTE: The method name is generated by replacing spaces with underscores. The result does not need to be a valid Ruby identifier though, the name may contain punctuation characters etc. That's because in Ruby technically any string may be a method name. Odd ones need define_method
and send
calls, but formally there's no restriction.
assert true
This line of code is called an assertion. An assertion is a line of code that evaluates an object (or expression) for expected results. For example, an assertion can check:
- does this value = that value?
- is this object nil?
- does this line of code throw an exception?
- is the user's password greater than 5 characters?
Every test contains one or more assertions. Only when all the assertions are successful will the test pass.
Maintaining the test database schema
In order to run your tests, your test database will need to have the current structure. The test helper checks whether your test database has any pending migrations. If so, it will try to load your db/schema.rb
or db/structure.sql
into the test database. If migrations are still pending, an error will be raised.
Running Tests
Running a test is as simple as invoking the file containing the test cases through rake test
command.
$ bin/rake test test/models/post_test.rb
.
Finished tests in 0.009262s, 107.9680 tests/s, 107.9680 assertions/s.
1 tests, 1 assertions, 0 failures, 0 errors, 0 skips
You can also run a particular test method from the test case by running the test and providing the test method name
.
$ bin/rake test test/models/post_test.rb test_the_truth
.
Finished tests in 0.009064s, 110.3266 tests/s, 110.3266 assertions/s.
1 tests, 1 assertions, 0 failures, 0 errors, 0 skips
This will run all test methods from the test case. Note that test_helper.rb
is in the test
directory, hence this directory needs to be added to the load path using the -I
switch.
The .
(dot) above indicates a passing test. When a test fails you see an F
; when a test throws an error you see an E
in its place. The last line of the output is the summary.
To see how a test failure is reported, you can add a failing test to the post_test.rb
test case.
test "should not save post without title" do
post = Post.new
assert_not post.save
end
Let us run this newly added test.
$ bin/rake test test/models/post_test.rb test_should_not_save_post_without_title
F
Finished tests in 0.044632s, 22.4054 tests/s, 22.4054 assertions/s.
1) Failure:
test_should_not_save_post_without_title(PostTest) [test/models/post_test.rb:6]:
Failed assertion, no message given.
1 tests, 1 assertions, 1 failures, 0 errors, 0 skips
In the output, F
denotes a failure. You can see the corresponding trace shown under 1)
along with the name of the failing test. The next few lines contain the stack trace followed by a message which mentions the actual value and the expected value by the assertion. The default assertion messages provide just enough information to help pinpoint the error. To make the assertion failure message more readable, every assertion provides an optional message parameter, as shown here:
test "should not save post without title" do
post = Post.new
assert_not post.save, "Saved the post without a title"
end
Running this test shows the friendlier assertion message:
1) Failure:
test_should_not_save_post_without_title(PostTest) [test/models/post_test.rb:6]:
Saved the post without a title
Now to get this test to pass we can add a model level validation for the title field.
class Post < ActiveRecord::Base
validates :title, presence: true
end
Now the test should pass. Let us verify by running the test again:
$ bin/rake test test/models/post_test.rb test_should_not_save_post_without_title
.
Finished tests in 0.047721s, 20.9551 tests/s, 20.9551 assertions/s.
1 tests, 1 assertions, 0 failures, 0 errors, 0 skips
Now, if you noticed, we first wrote a test which fails for a desired functionality, then we wrote some code which adds the functionality and finally we ensured that our test passes. This approach to software development is referred to as Test-Driven Development (TDD).
TIP: Many Rails developers practice Test-Driven Development (TDD). This is an excellent way to build up a test suite that exercises every part of your application. TDD is beyond the scope of this guide, but one place to start is with 15 TDD steps to create a Rails application.
To see how an error gets reported, here's a test containing an error:
test "should report error" do
# some_undefined_variable is not defined elsewhere in the test case
some_undefined_variable
assert true
end
Now you can see even more output in the console from running the tests:
$ bin/rake test test/models/post_test.rb test_should_report_error
E
Finished tests in 0.030974s, 32.2851 tests/s, 0.0000 assertions/s.
1) Error:
test_should_report_error(PostTest):
NameError: undefined local variable or method `some_undefined_variable' for #<PostTest:0x007fe32e24afe0>
test/models/post_test.rb:10:in `block in <class:PostTest>'
1 tests, 0 assertions, 0 failures, 1 errors, 0 skips
Notice the 'E' in the output. It denotes a test with error.
NOTE: The execution of each test method stops as soon as any error or an assertion failure is encountered, and the test suite continues with the next method. All test methods are executed in alphabetical order.
When a test fails you are presented with the corresponding backtrace. By default
Rails filters that backtrace and will only print lines relevant to your
application. This eliminates the framework noise and helps to focus on your
code. However there are situations when you want to see the full
backtrace. simply set the BACKTRACE
environment variable to enable this
behavior:
$ BACKTRACE=1 bin/rake test test/models/post_test.rb
What to Include in Your Unit Tests
Ideally, you would like to include a test for everything which could possibly break. It's a good practice to have at least one test for each of your validations and at least one test for every method in your model.
Available Assertions
By now you've caught a glimpse of some of the assertions that are available. Assertions are the worker bees of testing. They are the ones that actually perform the checks to ensure that things are going as planned.
There are a bunch of different types of assertions you can use.
Here's an extract of the assertions you can use with minitest
, the default testing library used by Rails. The [msg]
parameter is an optional string message you can specify to make your test failure messages clearer. It's not required.
Assertion | Purpose |
---|---|
assert( test, [msg] ) |
Ensures that test is true. |
assert_not( test, [msg] ) |
Ensures that test is false. |
assert_equal( expected, actual, [msg] ) |
Ensures that expected == actual is true. |
assert_not_equal( expected, actual, [msg] ) |
Ensures that expected != actual is true. |
assert_same( expected, actual, [msg] ) |
Ensures that expected.equal?(actual) is true. |
assert_not_same( expected, actual, [msg] ) |
Ensures that expected.equal?(actual) is false. |
assert_nil( obj, [msg] ) |
Ensures that obj.nil? is true. |
assert_not_nil( obj, [msg] ) |
Ensures that obj.nil? is false. |
assert_match( regexp, string, [msg] ) |
Ensures that a string matches the regular expression. |
assert_no_match( regexp, string, [msg] ) |
Ensures that a string doesn't match the regular expression. |
assert_in_delta( expecting, actual, [delta], [msg] ) |
Ensures that the numbers expected and actual are within delta of each other. |
assert_not_in_delta( expecting, actual, [delta], [msg] ) |
Ensures that the numbers expected and actual are not within delta of each other. |
assert_throws( symbol, [msg] ) { block } |
Ensures that the given block throws the symbol. |
assert_raises( exception1, exception2, ... ) { block } |
Ensures that the given block raises one of the given exceptions. |
assert_nothing_raised( exception1, exception2, ... ) { block } |
Ensures that the given block doesn't raise one of the given exceptions. |
assert_instance_of( class, obj, [msg] ) |
Ensures that obj is an instance of class . |
assert_not_instance_of( class, obj, [msg] ) |
Ensures that obj is not an instance of class . |
assert_kind_of( class, obj, [msg] ) |
Ensures that obj is or descends from class . |
assert_not_kind_of( class, obj, [msg] ) |
Ensures that obj is not an instance of class and is not descending from it. |
assert_respond_to( obj, symbol, [msg] ) |
Ensures that obj responds to symbol . |
assert_not_respond_to( obj, symbol, [msg] ) |
Ensures that obj does not respond to symbol . |
assert_operator( obj1, operator, [obj2], [msg] ) |
Ensures that obj1.operator(obj2) is true. |
assert_not_operator( obj1, operator, [obj2], [msg] ) |
Ensures that obj1.operator(obj2) is false. |
assert_send( array, [msg] ) |
Ensures that executing the method listed in array[1] on the object in array[0] with the parameters of array[2 and up] is true. This one is weird eh? |
flunk( [msg] ) |
Ensures failure. This is useful to explicitly mark a test that isn't finished yet. |
Because of the modular nature of the testing framework, it is possible to create your own assertions. In fact, that's exactly what Rails does. It includes some specialized assertions to make your life easier.
NOTE: Creating your own assertions is an advanced topic that we won't cover in this tutorial.
Rails Specific Assertions
Rails adds some custom assertions of its own to the test/unit
framework:
Assertion | Purpose |
---|---|
assert_difference(expressions, difference = 1, message = nil) {...} |
Test numeric difference between the return value of an expression as a result of what is evaluated in the yielded block. |
assert_no_difference(expressions, message = nil, &block) |
Asserts that the numeric result of evaluating an expression is not changed before and after invoking the passed in block. |
assert_recognizes(expected_options, path, extras={}, message=nil) |
Asserts that the routing of the given path was handled correctly and that the parsed options (given in the expected_options hash) match path. Basically, it asserts that Rails recognizes the route given by expected_options. |
assert_generates(expected_path, options, defaults={}, extras = {}, message=nil) |
Asserts that the provided options can be used to generate the provided path. This is the inverse of assert_recognizes. The extras parameter is used to tell the request the names and values of additional request parameters that would be in a query string. The message parameter allows you to specify a custom error message for assertion failures. |
assert_response(type, message = nil) |
Asserts that the response comes with a specific status code. You can specify :success to indicate 200-299, :redirect to indicate 300-399, :missing to indicate 404, or :error to match the 500-599 range. You can also pass an explicit status number or its symbolic equivalent. For more information, see full list of status codes and how their mapping works. |
assert_redirected_to(options = {}, message=nil) |
Assert that the redirection options passed in match those of the redirect called in the latest action. This match can be partial, such that assert_redirected_to(controller: "weblog") will also match the redirection of redirect_to(controller: "weblog", action: "show") and so on. You can also pass named routes such as assert_redirected_to root_path and Active Record objects such as assert_redirected_to @article . |
assert_template(expected = nil, message=nil) |
Asserts that the request was rendered with the appropriate template file. |
You'll see the usage of some of these assertions in the next chapter.
Functional Tests for Your Controllers
In Rails, testing the various actions of a single controller is called writing functional tests for that controller. Controllers handle the incoming web requests to your application and eventually respond with a rendered view.
What to Include in your Functional Tests
You should test for things such as:
- was the web request successful?
- was the user redirected to the right page?
- was the user successfully authenticated?
- was the correct object stored in the response template?
- was the appropriate message displayed to the user in the view?
Now that we have used Rails scaffold generator for our Post
resource, it has already created the controller code and tests. You can take look at the file posts_controller_test.rb
in the test/controllers
directory.
Let me take you through one such test, test_should_get_index
from the file posts_controller_test.rb
.
class PostsControllerTest < ActionController::TestCase
test "should get index" do
get :index
assert_response :success
assert_not_nil assigns(:posts)
end
end
In the test_should_get_index
test, Rails simulates a request on the action called index
, making sure the request was successful and also ensuring that it assigns a valid posts
instance variable.
The get
method kicks off the web request and populates the results into the response. It accepts 4 arguments:
- The action of the controller you are requesting. This can be in the form of a string or a symbol.
- An optional hash of request parameters to pass into the action (eg. query string parameters or post variables).
- An optional hash of session variables to pass along with the request.
- An optional hash of flash values.
Example: Calling the :show
action, passing an id
of 12 as the params
and setting a user_id
of 5 in the session:
get(:show, {'id' => "12"}, {'user_id' => 5})
Another example: Calling the :view
action, passing an id
of 12 as the params
, this time with no session, but with a flash message.
get(:view, {'id' => '12'}, nil, {'message' => 'booya!'})
NOTE: If you try running test_should_create_post
test from posts_controller_test.rb
it will fail on account of the newly added model level validation and rightly so.
Let us modify test_should_create_post
test in posts_controller_test.rb
so that all our test pass:
test "should create post" do
assert_difference('Post.count') do
post :create, post: {title: 'Some title'}
end
assert_redirected_to post_path(assigns(:post))
end
Now you can try running all the tests and they should pass.
Available Request Types for Functional Tests
If you're familiar with the HTTP protocol, you'll know that get
is a type of request. There are 6 request types supported in Rails functional tests:
get
post
patch
put
head
delete
All of request types are methods that you can use, however, you'll probably end up using the first two more often than the others.
NOTE: Functional tests do not verify whether the specified request type should be accepted by the action. Request types in this context exist to make your tests more descriptive.
The Four Hashes of the Apocalypse
After a request has been made using one of the 6 methods (get
, post
, etc.) and processed, you will have 4 Hash objects ready for use:
assigns
- Any objects that are stored as instance variables in actions for use in views.cookies
- Any cookies that are set.flash
- Any objects living in the flash.session
- Any object living in session variables.
As is the case with normal Hash objects, you can access the values by referencing the keys by string. You can also reference them by symbol name, except for assigns
. For example:
flash["gordon"] flash[:gordon]
session["shmession"] session[:shmession]
cookies["are_good_for_u"] cookies[:are_good_for_u]
# Because you can't use assigns[:something] for historical reasons:
assigns["something"] assigns(:something)
Instance Variables Available
You also have access to three instance variables in your functional tests:
@controller
- The controller processing the request@request
- The request@response
- The response
Setting Headers and CGI variables
HTTP headers
and
CGI variables
can be set directly on the @request
instance variable:
# setting a HTTP Header
@request.headers["Accept"] = "text/plain, text/html"
get :index # simulate the request with custom header
# setting a CGI variable
@request.headers["HTTP_REFERER"] = "http://example.com/home"
post :create # simulate the request with custom env variable
Testing Templates and Layouts
If you want to make sure that the response rendered the correct template and layout, you can use the assert_template
method:
test "index should render correct template and layout" do
get :index
assert_template :index
assert_template layout: "layouts/application"
end
Note that you cannot test for template and layout at the same time, with one call to assert_template
method.
Also, for the layout
test, you can give a regular expression instead of a string, but using the string, makes
things clearer. On the other hand, you have to include the "layouts" directory name even if you save your layout
file in this standard layout directory. Hence,
assert_template layout: "application"
will not work.
If your view renders any partial, when asserting for the layout, you have to assert for the partial at the same time. Otherwise, assertion will fail.
Hence:
test "new should render correct layout" do
get :new
assert_template layout: "layouts/application", partial: "_form"
end
is the correct way to assert for the layout when the view renders a partial with name _form
. Omitting the :partial
key in your assert_template
call will complain.
A Fuller Functional Test Example
Here's another example that uses flash
, assert_redirected_to
, and assert_difference
:
test "should create post" do
assert_difference('Post.count') do
post :create, post: {title: 'Hi', body: 'This is my first post.'}
end
assert_redirected_to post_path(assigns(:post))
assert_equal 'Post was successfully created.', flash[:notice]
end
Testing Views
Testing the response to your request by asserting the presence of key HTML elements and their content is a useful way to test the views of your application. The assert_select
assertion allows you to do this by using a simple yet powerful syntax.
NOTE: You may find references to assert_tag
in other documentation, but this is now deprecated in favor of assert_select
.
There are two forms of assert_select
:
assert_select(selector, [equality], [message])
ensures that the equality condition is met on the selected elements through the selector. The selector may be a CSS selector expression (String), an expression with substitution values, or an HTML::Selector
object.
assert_select(element, selector, [equality], [message])
ensures that the equality condition is met on all the selected elements through the selector starting from the element (instance of HTML::Node
) and its descendants.
For example, you could verify the contents on the title element in your response with:
assert_select 'title', "Welcome to Rails Testing Guide"
You can also use nested assert_select
blocks. In this case the inner assert_select
runs the assertion on the complete collection of elements selected by the outer assert_select
block:
assert_select 'ul.navigation' do
assert_select 'li.menu_item'
end
Alternatively the collection of elements selected by the outer assert_select
may be iterated through so that assert_select
may be called separately for each element. Suppose for example that the response contains two ordered lists, each with four list elements then the following tests will both pass.
assert_select "ol" do |elements|
elements.each do |element|
assert_select element, "li", 4
end
end
assert_select "ol" do
assert_select "li", 8
end
The assert_select
assertion is quite powerful. For more advanced usage, refer to its documentation.
Additional View-Based Assertions
There are more assertions that are primarily used in testing views:
Assertion | Purpose |
---|---|
assert_select_email |
Allows you to make assertions on the body of an e-mail. |
assert_select_encoded |
Allows you to make assertions on encoded HTML. It does this by un-encoding the contents of each element and then calling the block with all the un-encoded elements. |
css_select(selector) or css_select(element, selector) |
Returns an array of all the elements selected by the selector. In the second variant it first matches the base element and tries to match the selector expression on any of its children. If there are no matches both variants return an empty array. |
Here's an example of using assert_select_email
:
assert_select_email do
assert_select 'small', 'Please click the "Unsubscribe" link if you want to opt-out.'
end
Integration Testing
Integration tests are used to test the interaction among any number of controllers. They are generally used to test important work flows within your application.
Unlike Unit and Functional tests, integration tests have to be explicitly created under the 'test/integration' folder within your application. Rails provides a generator to create an integration test skeleton for you.
$ bin/rails generate integration_test user_flows
exists test/integration/
create test/integration/user_flows_test.rb
Here's what a freshly-generated integration test looks like:
require 'test_helper'
class UserFlowsTest < ActionDispatch::IntegrationTest
# test "the truth" do
# assert true
# end
end
Integration tests inherit from ActionDispatch::IntegrationTest
. This makes available some additional helpers to use in your integration tests. Also you need to explicitly include the fixtures to be made available to the test.
Helpers Available for Integration Tests
In addition to the standard testing helpers, there are some additional helpers available to integration tests:
Helper | Purpose |
---|---|
https? |
Returns true if the session is mimicking a secure HTTPS request. |
https! |
Allows you to mimic a secure HTTPS request. |
host! |
Allows you to set the host name to use in the next request. |
redirect? |
Returns true if the last request was a redirect. |
follow_redirect! |
Follows a single redirect response. |
request_via_redirect(http_method, path, [parameters], [headers]) |
Allows you to make an HTTP request and follow any subsequent redirects. |
post_via_redirect(path, [parameters], [headers]) |
Allows you to make an HTTP POST request and follow any subsequent redirects. |
get_via_redirect(path, [parameters], [headers]) |
Allows you to make an HTTP GET request and follow any subsequent redirects. |
patch_via_redirect(path, [parameters], [headers]) |
Allows you to make an HTTP PATCH request and follow any subsequent redirects. |
put_via_redirect(path, [parameters], [headers]) |
Allows you to make an HTTP PUT request and follow any subsequent redirects. |
delete_via_redirect(path, [parameters], [headers]) |
Allows you to make an HTTP DELETE request and follow any subsequent redirects. |
open_session |
Opens a new session instance. |
Integration Testing Examples
A simple integration test that exercises multiple controllers:
require 'test_helper'
class UserFlowsTest < ActionDispatch::IntegrationTest
fixtures :users
test "login and browse site" do
# login via https
https!
get "/login"
assert_response :success
post_via_redirect "/login", username: users(:david).username, password: users(:david).password
assert_equal '/welcome', path
assert_equal 'Welcome david!', flash[:notice]
https!(false)
get "/posts/all"
assert_response :success
assert assigns(:products)
end
end
As you can see the integration test involves multiple controllers and exercises the entire stack from database to dispatcher. In addition you can have multiple session instances open simultaneously in a test and extend those instances with assertion methods to create a very powerful testing DSL (domain-specific language) just for your application.
Here's an example of multiple sessions and custom DSL in an integration test
require 'test_helper'
class UserFlowsTest < ActionDispatch::IntegrationTest
fixtures :users
test "login and browse site" do
# User david logs in
david = login(:david)
# User guest logs in
guest = login(:guest)
# Both are now available in different sessions
assert_equal 'Welcome david!', david.flash[:notice]
assert_equal 'Welcome guest!', guest.flash[:notice]
# User david can browse site
david.browses_site
# User guest can browse site as well
guest.browses_site
# Continue with other assertions
end
private
module CustomDsl
def browses_site
get "/products/all"
assert_response :success
assert assigns(:products)
end
end
def login(user)
open_session do |sess|
sess.extend(CustomDsl)
u = users(user)
sess.https!
sess.post "/login", username: u.username, password: u.password
assert_equal '/welcome', sess.path
sess.https!(false)
end
end
end
Rake Tasks for Running your Tests
You don't need to set up and run your tests by hand on a test-by-test basis. Rails comes with a number of commands to help in testing. The table below lists all commands that come along in the default Rakefile when you initiate a Rails project.
Tasks | Description |
---|---|
rake test |
Runs all unit, functional and integration tests. You can also simply run rake as Rails will run all the tests by default |
rake test:controllers |
Runs all the controller tests from test/controllers |
rake test:functionals |
Runs all the functional tests from test/controllers , test/mailers , and test/functional |
rake test:helpers |
Runs all the helper tests from test/helpers |
rake test:integration |
Runs all the integration tests from test/integration |
rake test:mailers |
Runs all the mailer tests from test/mailers |
rake test:models |
Runs all the model tests from test/models |
rake test:units |
Runs all the unit tests from test/models , test/helpers , and test/unit |
rake test:all |
Runs all tests quickly by merging all types and not resetting db |
rake test:all:db |
Runs all tests quickly by merging all types and resetting db |
Brief Note About MiniTest
Ruby ships with a vast Standard Library for all common use-cases including testing. Ruby 1.8 provided Test::Unit
, a framework for unit testing in Ruby. All the basic assertions discussed above are actually defined in Test::Unit::Assertions
. The class ActiveSupport::TestCase
which we have been using in our unit and functional tests extends Test::Unit::TestCase
, allowing
us to use all of the basic assertions in our tests.
Ruby 1.9 introduced MiniTest
, an updated version of Test::Unit
which provides a backwards compatible API for Test::Unit
. You could also use MiniTest
in Ruby 1.8 by installing the minitest
gem.
NOTE: For more information on Test::Unit
, refer to test/unit Documentation
For more information on MiniTest
, refer to Minitest
Setup and Teardown
If you would like to run a block of code before the start of each test and another block of code after the end of each test you have two special callbacks for your rescue. Let's take note of this by looking at an example for our functional test in Posts
controller:
require 'test_helper'
class PostsControllerTest < ActionController::TestCase
# called before every single test
def setup
@post = posts(:one)
end
# called after every single test
def teardown
# as we are re-initializing @post before every test
# setting it to nil here is not essential but I hope
# you understand how you can use the teardown method
@post = nil
end
test "should show post" do
get :show, id: @post.id
assert_response :success
end
test "should destroy post" do
assert_difference('Post.count', -1) do
delete :destroy, id: @post.id
end
assert_redirected_to posts_path
end
end
Above, the setup
method is called before each test and so @post
is available for each of the tests. Rails implements setup
and teardown
as ActiveSupport::Callbacks
. Which essentially means you need not only use setup
and teardown
as methods in your tests. You could specify them by using:
- a block
- a method (like in the earlier example)
- a method name as a symbol
- a lambda
Let's see the earlier example by specifying setup
callback by specifying a method name as a symbol:
require 'test_helper'
class PostsControllerTest < ActionController::TestCase
# called before every single test
setup :initialize_post
# called after every single test
def teardown
@post = nil
end
test "should show post" do
get :show, id: @post.id
assert_response :success
end
test "should update post" do
patch :update, id: @post.id, post: {}
assert_redirected_to post_path(assigns(:post))
end
test "should destroy post" do
assert_difference('Post.count', -1) do
delete :destroy, id: @post.id
end
assert_redirected_to posts_path
end
private
def initialize_post
@post = posts(:one)
end
end
Testing Routes
Like everything else in your Rails application, it is recommended that you test your routes. An example test for a route in the default show
action of Posts
controller above should look like:
test "should route to post" do
assert_routing '/posts/1', {controller: "posts", action: "show", id: "1"}
end
Testing Your Mailers
Testing mailer classes requires some specific tools to do a thorough job.
Keeping the Postman in Check
Your mailer classes - like every other part of your Rails application - should be tested to ensure that it is working as expected.
The goals of testing your mailer classes are to ensure that:
- emails are being processed (created and sent)
- the email content is correct (subject, sender, body, etc)
- the right emails are being sent at the right times
From All Sides
There are two aspects of testing your mailer, the unit tests and the functional tests. In the unit tests, you run the mailer in isolation with tightly controlled inputs and compare the output to a known value (a fixture.) In the functional tests you don't so much test the minute details produced by the mailer; instead, we test that our controllers and models are using the mailer in the right way. You test to prove that the right email was sent at the right time.
Unit Testing
In order to test that your mailer is working as expected, you can use unit tests to compare the actual results of the mailer with pre-written examples of what should be produced.
Revenge of the Fixtures
For the purposes of unit testing a mailer, fixtures are used to provide an example of how the output should look. Because these are example emails, and not Active Record data like the other fixtures, they are kept in their own subdirectory apart from the other fixtures. The name of the directory within test/fixtures
directly corresponds to the name of the mailer. So, for a mailer named UserMailer
, the fixtures should reside in test/fixtures/user_mailer
directory.
When you generated your mailer, the generator creates stub fixtures for each of the mailers actions. If you didn't use the generator you'll have to make those files yourself.
The Basic Test Case
Here's a unit test to test a mailer named UserMailer
whose action invite
is used to send an invitation to a friend. It is an adapted version of the base test created by the generator for an invite
action.
require 'test_helper'
class UserMailerTest < ActionMailer::TestCase
test "invite" do
# Send the email, then test that it got queued
email = UserMailer.create_invite('me@example.com',
'friend@example.com', Time.now).deliver
assert_not ActionMailer::Base.deliveries.empty?
# Test the body of the sent email contains what we expect it to
assert_equal ['me@example.com'], email.from
assert_equal ['friend@example.com'], email.to
assert_equal 'You have been invited by me@example.com', email.subject
assert_equal read_fixture('invite').join, email.body.to_s
end
end
In the test we send the email and store the returned object in the email
variable. We then ensure that it was sent (the first assert), then, in the
second batch of assertions, we ensure that the email does indeed contain what we
expect. The helper read_fixture
is used to read in the content from this file.
Here's the content of the invite
fixture:
Hi friend@example.com,
You have been invited.
Cheers!
This is the right time to understand a little more about writing tests for your
mailers. The line ActionMailer::Base.delivery_method = :test
in
config/environments/test.rb
sets the delivery method to test mode so that
email will not actually be delivered (useful to avoid spamming your users while
testing) but instead it will be appended to an array
(ActionMailer::Base.deliveries
).
NOTE: The ActionMailer::Base.deliveries
array is only reset automatically in
ActionMailer::TestCase
tests. If you want to have a clean slate outside Action
Mailer tests, you can reset it manually with:
ActionMailer::Base.deliveries.clear
Functional Testing
Functional testing for mailers involves more than just checking that the email body, recipients and so forth are correct. In functional mail tests you call the mail deliver methods and check that the appropriate emails have been appended to the delivery list. It is fairly safe to assume that the deliver methods themselves do their job. You are probably more interested in whether your own business logic is sending emails when you expect them to go out. For example, you can check that the invite friend operation is sending an email appropriately:
require 'test_helper'
class UserControllerTest < ActionController::TestCase
test "invite friend" do
assert_difference 'ActionMailer::Base.deliveries.size', +1 do
post :invite_friend, email: 'friend@example.com'
end
invite_email = ActionMailer::Base.deliveries.last
assert_equal "You have been invited by me@example.com", invite_email.subject
assert_equal 'friend@example.com', invite_email.to[0]
assert_match(/Hi friend@example.com/, invite_email.body)
end
end
Testing helpers
In order to test helpers, all you need to do is check that the output of the
helper method matches what you'd expect. Tests related to the helpers are
located under the test/helpers
directory. Rails provides a generator which
generates both the helper and the test file:
$ bin/rails generate helper User
create app/helpers/user_helper.rb
invoke test_unit
create test/helpers/user_helper_test.rb
The generated test file contains the following code:
require 'test_helper'
class UserHelperTest < ActionView::TestCase
end
A helper is just a simple module where you can define methods which are available into your views. To test the output of the helper's methods, you just have to use a mixin like this:
class UserHelperTest < ActionView::TestCase
include UserHelper
test "should return the user name" do
# ...
end
end
Moreover, since the test class extends from ActionView::TestCase
, you have
access to Rails' helper methods such as link_to
or pluralize
.
Other Testing Approaches
The built-in test/unit
based testing is not the only way to test Rails applications. Rails developers have come up with a wide variety of other approaches and aids for testing, including:
- NullDB, a way to speed up testing by avoiding database use.
- Factory Girl, a replacement for fixtures.
- Machinist, another replacement for fixtures.
- Fixture Builder, a tool that compiles Ruby factories into fixtures before a test run.
- MiniTest::Spec Rails, use the MiniTest::Spec DSL within your rails tests.
- Shoulda, an extension to
test/unit
with additional helpers, macros, and assertions. - RSpec, a behavior-driven development framework