View Source Testing Custom Checks
Credo.Test.Case
provides conveniences for testing Credo custom checks and plugins.
This module can be used in your test cases, like this:
use Credo.Test.Case
Using this module will:
- import all the functions from this module
- make the test case
:async
by default (useasync: false
to opt out of this behaviour)
In test_helper.exs
, make sure credo
is started:
{:ok, _} = Application.ensure_all_started(:credo)
Let's test the RejectModuleAttributes
check that we implemented in Adding custom checks.
Basic custom check tests
To test a check, we can use Credo.Test.Case
for convenience:
defmodule MyProject.Checks.RejectModuleAttributesTest do
use Credo.Test.Case
alias MyProject.Checks.RejectModuleAttributes
test "it should NOT report expected code" do
"""
defmodule CredoSampleModule do
@somedoc "This is somedoc"
end
"""
|> to_source_file()
|> run_check(RejectModuleAttributes)
|> refute_issues()
end
test "it should report code that includes rejected module attribute names" do
"""
defmodule CredoSampleModule do
@checkdoc "This is checkdoc"
end
"""
|> to_source_file()
|> run_check(RejectModuleAttributes)
|> assert_issues()
end
end
We have two tests: one for the good case, one for the bad case. In each, we create a source file representation from a heredoc, run our custom check and assert/refute the issues we expect.
Using custom params in tests
We can (and should) also test the params of our check by passing them to run_check/2
:
defmodule MyProject.Checks.RejectModuleAttributesTest do
use Credo.Test.Case
alias MyProject.Checks.RejectModuleAttributes
# ...
test "it should NOT report code that includes default rejected module attribute names when a custom set of rejected names is provided" do
"""
defmodule CredoSampleModule do
@checkdoc "This is checkdoc"
end
"""
|> to_source_file()
|> run_check(RejectModuleAttributes, reject: [:somedoc])
|> refute_issues()
end
test "it should report expected code when a custom set of rejected names is provided" do
"""
defmodule CredoSampleModule do
@somedoc "This is somedoc"
end
"""
|> to_source_file()
|> run_check(RejectModuleAttributes, reject: [:somedoc])
|> assert_issues()
end
end
Asserting found issues
Once we get to know domain a little better, we can add more tests, typically testing for other bad cases in which our check should produce issues.
Note that there are two assertion functions for this: assert_issue/2
and assert_issues/2
, where the first one
ensures that there is a single issue and the second asserts that there are at least two issues.
Both functions take an optional callback
as their second parameter, which is called with the issue
or the
list of issues
found, which makes it convenient to check for the issues properties ...
"""
# ... any Elixir code ...
"""
|> to_source_file()
|> run_check(RejectModuleAttributes)
|> assert_issue(fn issue -> assert issue.trigger == "@checkdoc" end)
... or properties of the list of issues:
"""
# ... any Elixir code ...
"""
|> to_source_file()
|> run_check(RejectModuleAttributes)
|> assert_issues(fn issues -> assert Enum.count(issues) == 3 end)
Testing checks that analyse multiple source files
For checks that analyse multiple source files, like Credo's consistency checks, we can use to_source_files/1
to
create
[
"""
# source file 1
""",
"""
# source file 2
"""
]
|> to_source_files()
|> run_check(RejectModuleAttributes)
|> refute_issues()
If our check needs named source files, we can always use to_source_file/2
to create individually named source
files and combine them into a list:
source_file1 =
"""
# source file 1
"""
|> to_source_file("foo.ex")
source_file2 =
"""
# source file 2
"""
|> to_source_file("bar.ex")
[source_file1, source_file2]
|> run_check(RejectModuleAttributes)
|> assert_issue(fn issue -> assert issue.filename == "foo.ex" end)