View Source ExUnit.Case (ExUnit v1.15.4)
Helpers for defining test cases.
This module must be used in other modules as a way to configure and prepare them for testing.
When used, it accepts the following options:
:async
- configures tests in this module to run concurrently with tests in other modules. Tests in the same module never run concurrently. It should be enabled only if tests do not change any global state. Defaults tofalse
.:register
- whenfalse
, does not register this module within ExUnit server. This means the module won't run when ExUnit suite runs.
use ExUnit.Case
When you
use ExUnit.Case
, it will import the functionality fromExUnit.Assertions
,ExUnit.Callbacks
,ExUnit.DocTest
, and this module itself.
Examples
defmodule AssertionTest do
# Use the module
use ExUnit.Case, async: true
# The "test" macro is imported by ExUnit.Case
test "always pass" do
assert true
end
end
Context
All tests receive a context as an argument. The context is particularly useful for sharing information between callbacks and tests:
defmodule KVTest do
use ExUnit.Case
setup do
{:ok, pid} = KV.start_link()
{:ok, pid: pid}
end
test "stores key-value pairs", context do
assert KV.put(context[:pid], :hello, :world) == :ok
assert KV.get(context[:pid], :hello) == :world
end
end
As the context is a map, it can be pattern matched on to extract information:
test "stores key-value pairs", %{pid: pid} = _context do
assert KV.put(pid, :hello, :world) == :ok
assert KV.get(pid, :hello) == :world
end
Tags
The context is used to pass information from the callbacks to the test. In order to pass information from the test to the callback, ExUnit provides tags.
By tagging a test, the tag value can be accessed in the context, allowing the developer to customize the test. Let's see an example:
defmodule FileTest do
# Changing directory cannot be async
use ExUnit.Case, async: false
setup context do
# Read the :cd tag value
if cd = context[:cd] do
prev_cd = File.cwd!()
File.cd!(cd)
on_exit(fn -> File.cd!(prev_cd) end)
end
:ok
end
@tag cd: "fixtures"
test "reads UTF-8 fixtures" do
File.read("README.md")
end
end
In the example above, we have defined a tag called :cd
that is
read in the setup callback to configure the working directory the
test is going to run on.
Tags are also very effective when used with case templates
(ExUnit.CaseTemplate
) allowing callbacks in the case template
to customize the test behaviour.
Note a tag can be set in two different ways:
@tag key: value
@tag :key # equivalent to setting @tag key: true
If a tag is given more than once, the last value wins.
Module and describe tags
A tag can be set for all tests in a module or describe block by
setting @moduletag
or @describetag
inside each context
respectively:
defmodule ApiTest do
use ExUnit.Case
@moduletag :external
describe "makes calls to the right endpoint" do
@describetag :endpoint
# ...
end
end
If you are setting a @moduletag
or @describetag
attribute, you must
set them after your call to use ExUnit.Case
otherwise you will see
compilation errors.
If the same key is set via @tag
, the @tag
value has higher
precedence.
The setup_all
blocks only receive tags that are set using @moduletag
.
Known tags
The following tags are set automatically by ExUnit and are therefore reserved:
:module
- the module on which the test was defined:file
- the file on which the test was defined:line
- the line on which the test was defined:test
- the test name:async
- if the test case is in async mode:registered
- used forExUnit.Case.register_attribute/3
values:describe
- the describe block the test belongs to:describe_line
- the line the describe block begins on:doctest
- the module or the file being doctested (if a doctest):doctest_line
- the line the doctest was defined (if a doctest):doctest_data
- additional metadata about doctests (if a doctest):test_type
- the test type used when printing test results. It is set by ExUnit to:test
,:doctest
and so on, but is customizable.
The following tags customize how tests behave:
:capture_log
- see the "Log Capture" section below:skip
- skips the test with the given reason:timeout
- customizes the test timeout in milliseconds (defaults to 60000). Accepts:infinity
as a timeout value.:tmp_dir
- (since v1.11.0) see the "Tmp Dir" section below
Filters
Tags can also be used to identify specific tests, which can then
be included or excluded using filters. The most common functionality
is to exclude some particular tests from running, which can be done
via ExUnit.configure/1
:
# Exclude all external tests from running
ExUnit.configure(exclude: [external: true])
From now on, ExUnit will not run any test that has the :external
option
set to true
. This behaviour can be reversed with the :include
option
which is usually passed through the command line:
$ mix test --include external:true
Run mix help test
for more information on how to run filters via Mix.
Another use case for tags and filters is to exclude all tests that have a particular tag by default, regardless of its value, and include only a certain subset:
ExUnit.configure(exclude: :os, include: [os: :unix])
A given include/exclude filter can be given more than once:
ExUnit.configure(exclude: [os: :unix, os: :windows])
Keep in mind that all tests are included by default, so unless they are
excluded first, the include
option has no effect.
Log Capture
ExUnit can optionally suppress printing of log messages that are generated during a test. Log messages generated while running a test are captured and only if the test fails are they printed to aid with debugging.
You can opt into this behaviour for individual tests by tagging them with
:capture_log
or enable log capture for all tests in the ExUnit configuration:
ExUnit.start(capture_log: true)
This default can be overridden by @tag capture_log: false
or
@moduletag capture_log: false
.
Since setup_all
blocks don't belong to a specific test, log messages generated
in them (or between tests) are never captured. If you want to suppress these
messages as well, remove the console backend globally by setting:
config :logger, backends: []
Tmp Dir
ExUnit automatically creates a temporary directory for tests tagged with
:tmp_dir
and puts the path to that directory into the test context.
The directory is removed before being created to ensure we start with a blank
slate.
The temporary directory path is unique (includes the test module and test name)
and thus appropriate for running tests concurrently. You can customize the path
further by setting the tag to a string, e.g.: tmp_dir: "my_path"
, which would
make the final path to be: tmp/<module>/<test>/my_path
.
Example:
defmodule MyTest do
use ExUnit.Case, async: true
@tag :tmp_dir
test "with tmp_dir", %{tmp_dir: tmp_dir} do
assert tmp_dir =~ "with tmp_dir"
assert File.dir?(tmp_dir)
end
end
As with other tags, :tmp_dir
can also be set as @moduletag
and
@describetag
.
Summary
Functions
Describes tests together.
Returns the most recently registered test case as an %ExUnit.Test{}
struct.
Registers a new attribute to be used during ExUnit.Case
tests.
Registers a new describe attribute to be used during ExUnit.Case
tests.
Registers a new module attribute to be used during ExUnit.Case
tests.
Registers a test with the given environment.
Registers a function to run as part of this case.
Defines a not implemented test with a string.
Defines a test with message
.
Types
@type env() :: module() | Macro.Env.t()
Functions
Describes tests together.
Every describe block receives a name which is used as prefix for
upcoming tests. Inside a block, ExUnit.Callbacks.setup/1
may be
invoked and it will define a setup callback to run only for the
current block. The describe name is also added as a tag, allowing
developers to run tests for specific blocks.
Examples
defmodule StringTest do
use ExUnit.Case, async: true
describe "String.capitalize/1" do
test "first grapheme is in uppercase" do
assert String.capitalize("hello") == "Hello"
end
test "converts remaining graphemes to lowercase" do
assert String.capitalize("HELLO") == "Hello"
end
end
end
When using Mix, you can run all tests in a describe block by name:
$ mix test --only describe:"String.capitalize/1"
or by passing the exact line the describe block starts on:
$ mix test path/to/file:123
Note describe blocks cannot be nested. Instead of relying on hierarchy for composition, developers should build on top of named setups. For example:
defmodule UserManagementTest do
use ExUnit.Case, async: true
describe "when user is logged in and is an admin" do
setup [:log_user_in, :set_type_to_admin]
test ...
end
describe "when user is logged in and is a manager" do
setup [:log_user_in, :set_type_to_manager]
test ...
end
defp log_user_in(context) do
# ...
end
end
By forbidding hierarchies in favor of named setups, it is straightforward for the developer to glance at each describe block and know exactly the setup steps involved.
@spec get_last_registered_test(env()) :: ExUnit.Test.t() | nil
Returns the most recently registered test case as an %ExUnit.Test{}
struct.
This is used by third-party utilities to allow compile-time configuration using test tags without having to explicitly pass the test context at run-time. It is intended to be invoked in macros before the test module is compiled.
Raises if called with a module that has already been compiled.
Registers a new attribute to be used during ExUnit.Case
tests.
The attribute values will be available through context.registered
.
Registered values are cleared after each test/3
similar
to @tag
.
This function takes the same options as Module.register_attribute/3
.
Examples
defmodule MyTest do
use ExUnit.Case
ExUnit.Case.register_attribute(__MODULE__, :fixtures, accumulate: true)
@fixtures :user
@fixtures {:post, insert: false}
test "using custom attribute", context do
assert context.registered.fixtures == [{:post, insert: false}, :user]
end
test "custom attributes are cleared per test", context do
assert context.registered.fixtures == []
end
end
Registers a new describe attribute to be used during ExUnit.Case
tests.
The attribute values will be available through context.registered
.
Registered values are cleared after each describe/2
similar
to @describetag
.
This function takes the same options as Module.register_attribute/3
.
Examples
defmodule MyTest do
use ExUnit.Case
ExUnit.Case.register_describe_attribute(__MODULE__, :describe_fixtures, accumulate: true)
describe "using custom attribute" do
@describe_fixtures :user
@describe_fixtures {:post, insert: false}
test "has attribute", context do
assert context.registered.describe_fixtures == [{:post, insert: false}, :user]
end
end
describe "custom attributes are cleared per describe" do
test "doesn't have attributes", context do
assert context.registered.describe_fixtures == []
end
end
end
Registers a new module attribute to be used during ExUnit.Case
tests.
The attribute values will be available through context.registered
.
This function takes the same options as Module.register_attribute/3
.
Examples
defmodule MyTest do
use ExUnit.Case
ExUnit.Case.register_module_attribute(__MODULE__, :module_fixtures, accumulate: true)
@module_fixtures :user
@module_fixtures {:post, insert: false}
test "using custom attribute", context do
assert context.registered.module_fixtures == [{:post, insert: false}, :user]
end
test "still using custom attribute", context do
assert context.registered.module_fixtures == [{:post, insert: false}, :user]
end
end
Registers a test with the given environment.
This function is deprecated in favor of register_test/6
which performs
better under tight loops by avoiding __ENV__
.
register_test(mod, file, line, test_type, name, tags)
View Source (since 1.10.0)Registers a function to run as part of this case.
This is used by third-party projects, like QuickCheck, to
implement macros like property/3
that works like test
but instead defines a property. See test/3
implementation
for an example of invoking this function.
The test type will be converted to a string and pluralized for
display. You can use ExUnit.plural_rule/2
to set a custom
pluralization.
Defines a not implemented test with a string.
Provides a convenient macro that allows a test to be defined
with a string, but not yet implemented. The resulting test will
always fail and print a "Not implemented" error message. The
resulting test case is also tagged with :not_implemented
.
Examples
test "this will be a test in future"
Defines a test with message
.
The test may also define a pattern, which will be matched
against the test context. For more information on contexts, see
ExUnit.Callbacks
.
Examples
test "true is equal to true" do
assert true == true
end