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. You can find comprehensive documentation in the fixture api documentation.
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
Note: For associations to reference one another by name, you cannot specify
the id:
attribute on the fixtures. Rails will auto assign a
primary key to be consistent between runs. If you manually specify an
id:
attribute, this behavior will not work. For more
information on this association behavior please read the fixture
api documentation.
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 article title:string body:text ... create app/models/article.rb create test/models/article_test.rb create test/fixtures/articles.yml ...
The default test stub in test/models/article_test.rb
looks
like this:
require 'test_helper' class ArticleTest < 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 ArticleTest < ActiveSupport::TestCase
The ArticleTest
class defines a test case because it
inherits from ActiveSupport::TestCase
.
ArticleTest
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::Test
(which is the superclass of
ActiveSupport::TestCase
) that begins with test_
(case sensitive) is simply called a test. So, test_password
and test_valid_password
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. Usually
this indicates that your schema is not fully migrated. Running the
migrations against the development database (bin/rake
db:migrate
) will bring the schema up to date.
NOTE: If existing migrations required modifications, the test database
needs to be rebuilt. This can be done by executing bin/rake
db:test:prepare
.
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/article_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/article_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
article_test.rb
test case.
test "should not save article without title" do article = Article.new assert_not article.save end
Let us run this newly added test.
$ bin/rake test test/models/article_test.rb test_should_not_save_article_without_title F Finished tests in 0.044632s, 22.4054 tests/s, 22.4054 assertions/s. 1) Failure: test_should_not_save_article_without_title(ArticleTest) [test/models/article_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 article without title" do article = Article.new assert_not article.save, "Saved the article without a title" end
Running this test shows the friendlier assertion message:
1) Failure: test_should_not_save_article_without_title(ArticleTest) [test/models/article_test.rb:6]: Saved the article without a title
Now to get this test to pass we can add a model level validation for the title field.
class Article < 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/article_test.rb test_should_not_save_article_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/article_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(ArticleTest): NameError: undefined local variable or method `some_undefined_variable' for #<ArticleTest:0x007fe32e24afe0> test/models/article_test.rb:10:in `block in <class:ArticleTest>' 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/article_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_empty( obj, [msg] )
| Ensures that obj
is empty?
.| |
assert_not_empty( obj, [msg] )
| Ensures that obj
is not empty?
.| | 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_includes(
collection, obj, [msg] )
| Ensures that obj
is in
collection
.| | assert_not_includes( collection, obj,
[msg] )
| Ensures that obj
is not in
collection
.| | 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_predicate (
obj, predicate, [msg] )
| Ensures that obj.predicate
is
true, e.g. assert_predicate str, :empty?
| |
assert_not_predicate ( obj, predicate, [msg] )
| Ensures that
obj.predicate
is false, e.g. assert_not_predicate str,
:empty?
| | 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.|
The above are subset of assertions that minitest supports. For an exhaustive & more up-to-date list, please check Minitest API documentation, specifically Minitest::Assertions
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 minitest
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}[http://rubydoc.info/github/rack/rack/master/Rack/Utils#HTTP_STATUS_CODES-constant]
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 Article
resource, it has already created the controller code and tests. You can
take look at the file articles_controller_test.rb
in the
test/controllers
directory.
Let me take you through one such test, test_should_get_index
from the file articles_controller_test.rb
.
class ArticlesControllerTest < ActionController::TestCase test "should get index" do get :index assert_response :success assert_not_nil assigns(:articles) 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 articles
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 article 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_article
test from
articles_controller_test.rb
it will fail on account of the
newly added model level validation and rightly so.
Let us modify test_should_create_article
test in
articles_controller_test.rb
so that all our test pass:
test "should create article" do assert_difference('Article.count') do post :create, article: {title: 'Some title'} end assert_redirected_to article_path(assigns(:article)) 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
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 article" do assert_difference('Article.count') do post :create, article: {title: 'Hi', body: 'This is my first article.'} end assert_redirected_to article_path(assigns(:article)) assert_equal 'Article 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. This has been removed in 4.2. Use assert_select
instead.
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) or an
expression with substitution values.
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
Nokogiri::XML::Node
or Nokogiri::XML::NodeSet
)
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 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 "/articles/all" assert_response :success assert assigns(:articles) 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 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¶ ↑
Rails comes with a number of built-in rake tasks to help with testing. The table below lists the commands included in the default Rakefile when a Rails project is created.
| Tasks | Description | | ———————– | ———– | | rake test
| Runs
all tests in the test
folder. 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:jobs
| Runs all the job tests from test/jobs
| |
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:db
| Runs all tests in the test
folder and resets
the db |
A Brief Note About Minitest¶ ↑
Ruby ships with a vast Standard Library for all common use-cases including
testing. Since version 1.9, Ruby provides Minitest
, a
framework for testing. All the basic assertions such as
assert_equal
discussed above are actually defined in
Minitest::Assertions
. The classes
ActiveSupport::TestCase
,
ActionController::TestCase
,
ActionMailer::TestCase
, ActionView::TestCase
and
ActionDispatch::IntegrationTest
- which we have been
inheriting in our test classes - include Minitest::Assertions
,
allowing us to use all of the basic assertions in our tests.
NOTE: 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 Articles
controller:
require 'test_helper' class ArticlesControllerTest < ActionController::TestCase # called before every single test def setup @article = articles(:one) end # called after every single test def teardown # as we are re-initializing @article before every test # setting it to nil here is not essential but I hope # you understand how you can use the teardown method @article = nil end test "should show article" do get :show, id: @article.id assert_response :success end test "should destroy article" do assert_difference('Article.count', -1) do delete :destroy, id: @article.id end assert_redirected_to articles_path end end
Above, the setup
method is called before each test and so
@article
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 ArticlesControllerTest < ActionController::TestCase # called before every single test setup :initialize_article # called after every single test def teardown @article = nil end test "should show article" do get :show, id: @article.id assert_response :success end test "should update article" do patch :update, id: @article.id, article: {} assert_redirected_to article_path(assigns(:article)) end test "should destroy article" do assert_difference('Article.count', -1) do delete :destroy, id: @article.id end assert_redirected_to articles_path end private def initialize_article @article = articles(:one) end end
Testing Routes¶ ↑
Like everything else in your Rails application, it is recommended that you
test your routes. Below are example tests for the routes of default
show
and create
action of Articles
controller above and it should look like:
class ArticleRoutesTest < ActionController::TestCase test "should route to article" do assert_routing '/articles/1', { controller: "articles", action: "show", id: "1" } end test "should route to create article" do assert_routing({ method: 'post', path: '/articles' }, { controller: "articles", action: "create" }) end 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.
If you generated your mailer, the generator does not create stub fixtures for the mailers actions. You'll have to create those files yourself as described above.
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_now 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.to_s) 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.
A helper test looks like so:
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
.
Testing Jobs¶ ↑
Since your custom jobs can be queued at different levels inside your application, you'll need to test both jobs themselves (their behavior when they get enqueued) and that other entities correctly enqueue them.
A Basic Test Case¶ ↑
By default, when you generate a job, an associated test will be generated
as well under the test/jobs
directory. Here's an example
test with a billing job:
require 'test_helper' class BillingJobTest < ActiveJob::TestCase test 'that account is charged' do BillingJob.perform_now(account, product) assert account.reload.charged_for?(product) end end
This test is pretty simple and only asserts that the job get the work done as expected.
By default, ActiveJob::TestCase
will set the queue adapter to
:test
so that your jobs are performed inline. It will also
ensure that all previously performed and enqueued jobs are cleared before
any test run so you can safely assume that no jobs have already been
executed in the scope of each test.
Custom Assertions And Testing Jobs Inside Other Components¶ ↑
Active Job ships with a bunch of custom assertions that can be used to lessen the verbosity of tests:
| Assertion | Purpose | | ————————————– | ——- | |
assert_enqueued_jobs(number)
| Asserts that the number of
enqueued jobs matches the given number. | |
assert_performed_jobs(number)
| Asserts that the number of
performed jobs matches the given number. | | assert_no_enqueued_jobs
{ ... }
| Asserts that no jobs have been enqueued. | |
assert_no_performed_jobs { ... }
| Asserts that no jobs have
been performed. | | assert_enqueued_with([args]) { ... }
|
Asserts that the job passed in the block has been enqueued with the given
arguments. | | assert_performed_with([args]) { ... }
| Asserts
that the job passed in the block has been performed with the given
arguments. |
It's a good practice to ensure that your jobs correctly get enqueued or performed wherever you invoke them (e.g. inside your controllers). This is precisely where the custom assertions provided by Active Job are pretty useful. For instance, within a model:
require 'test_helper' class ProductTest < ActiveJob::TestCase test 'billing job scheduling' do assert_enqueued_with(job: BillingJob) do product.charge(account) end end end
Other Testing Approaches¶ ↑
The built-in minitest
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.
-
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
-
Capybara, Acceptance test framework for web applications