Running Tests

The Clojure ecosystem provides a lot of support for test-driven development (TDD) and other test-centric patterns. First, Clojure provides a standardized framework for developing tests called clojure.test. Many other testing libraries plug into this framework. Second, tools like Leiningen create standardized application and library project structures that provide locations and idiomatic naming for test code. Finally, CIDER provides several easy ways to run these tests, view the test results, and quickly jump to code that is failing to pass a given test.

CIDER only supports clojure.test and other libraries providing integration with clojure.test. Native support for other libraries might be available via CIDER plugins.

Basic Usage

CIDER has several functions that help you run all your tests or a selected subset of them. All of the CIDER test commands are available in both source code and REPL buffers. In REPL buffers you can also use , to invoke some of the testing commands.

CIDER will only run tests that have been loaded (evaluated). This means that prior to running some tests you always have to evaluate them first. As a corollary - if you make some changes to a test, you’ll have to re-evaluate it, so that CIDER will pick up the updated version.

First, you can run all the tests in your project with C-c C-t p or C-c C-t C-p. It’s important to realize that this will load all the namespaces in your project, which might be more than you’re expecting.

You can run all loaded tests with C-c C-t l or C-c C-t C-l.

If you invoke either of these commands with a prefix (e.g. C-u C-c C-t l), CIDER will prompt for test selector filters and only run those tests that match the selector inclusions/exclusions.

Test Selectors

Test developers use selectors to define subsets of the total test suite that are run together for different testing tasks. For example you can mark some of your tests with the ^:smoke metadata marker and others with ^:integration. This enables you to run these tests separately in your build pipeline. CIDER helps you to run these same test subsets in your development environment.

Test selectors were originally a leiningen feature and you can get more information by executing:

$ lein help test

You can run all the tests in the current namespace, whether specified by a source file or by the REPL, using C-c C-t n or C-c C-t C-n. Note that it’s idiomatic for Clojure projects to locate tests in a separate namespace than the code that is being tested. CIDER uses a simple algorithm to figure out where the tests are located. The algorithm works as follows:

  • If you’re in an implementation namespace (e.g. some.ns), CIDER will try to find a matching test namespace (by default some.ns-test) and run the tests there.

  • If you’re in something that already looks like a test namespace (e.g. some.ns-test), CIDER will simply run the tests in that namespace.

If you have put some of your tests into your implementation namespace, using clojure.test/with-test, for instance, you might want to suppress the namespace inference logic and force CIDER to run tests in the current namespace unconditionally. You can do this by adding a prefix to the namespace commands: C-u C-c C-t C-n. This will simply run whatever tests are present in the currently visited or active namespace.

You can also run a subset of the tests defined in the namespace, filtered by test selectors, using C-c C-t C-s. CIDER will prompt for the selectors in the minibuffer. If you call this command with a prefix (C-u C-c C-t C-s) you can suppress the namespace inference logic as for C-u C-c C-t C-n

Finally, you can execute the specific test at the point using C-c C-t t or C-c C-t C-t. It will also work for implementation functions, by searching for a matching test namespace with a matching deftest name.


You can configure CIDER’s test execution behavior in multiple ways.


Starting from 1.8.0, CIDER has standard fail-fast functionality, controlled by the cider-test-fail-fast defcustom (default t).

You can toggle its value for the current buffer using cider-test-toggle-fail-fast (C-c C-t f or C-c C-t C-f)

fail-fast will never be chosen for the "retest" functionality, since that would cause you to lose the majority of the tests that previously failed.

Test Namespace Naming Convention

If your tests are not following the some.ns-test naming convention you can set the variable cider-test-infer-test-ns to a function that takes the current namespace and returns the matching test namespace (which may be the same as the current namespace). This provides complete flexibility to structure your test suite using whatever conventions you might want. Here’s how you can configure the test running to look for some.test-ns instead of some.ns-test:

(defun cider-custom-test-ns-fn (ns)
  "For a NS, return the test namespace, which may be the argument itself.
This uses the convention of prepending 'test-' to the namespace name."
  (when ns
    (let ((prefix "test-"))
      (if (string-prefix-p prefix ns)
        (concat prefix ns)))))

(setq cider-test-infer-test-ns #'cider-custom-test-ns-fn)

Default Test Selectors

If you have selectors you want automatically applied, you can set the variables cider-test-default-include-selectors and cider-test-default-exclude-selectors to a list of strings to use. The following is an example of setting the default exclude selectors so that tests tagged as "integration" or "flakey" don’t run.

(setq cider-test-default-exclude-selectors '("integration" "flakey"))
You’ll generally want to place default selectors in your project configuration, as opposed to your global configuration.

Display Test Report on Success

By default the test report is displayed only when there are test failures or errors. If you want to view the test report regardless of whether the tests have passed or failed:

(setq cider-test-show-report-on-success t)

Running a callback on errors

Sometimes, for fine-grained integrations or debugging, you might want to run an arbitrary callback whenever the tests fail due to an exception.

For this, you can safely redefine cider.nrepl.middleware.test/test-error-handler using vanilla Clojure; please refer to its docstring for more details.

Running Tests Automatically (Test-Driven Development)

CIDER provides a minor-mode that automatically runs all tests for a namespace whenever you load a file (with C-c C-k). You can toggle it manually with M-x cider-auto-test-mode, or you can use:

(cider-auto-test-mode 1)

This is identical to manually typing C-c C-t C-n every time you load a Clojure buffer. As described previously, CIDER will try to automatically determine the namespace containing the tests.