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3. Configuration


Kaocha is configured through a tests.edn file, typically placed in the root of the project. Many options can also be specified on the command line, in which case they take precedence.

Reading tests.edn and combining it with command line flags yields the Test Configuration, which is the first main type of data structure that Kaocha uses. It contains a description of the test suites to run, the plugins to execute, as well as various options and flags.

Here's an example test configuration with a single test suite:

{:kaocha/tests                       [{:kaocha.testable/type :kaocha.type/clojure.test
                                       :kaocha.testable/id   :unit
                                       :kaocha/ns-patterns   ["-test$"]
                                       :kaocha/source-paths  ["src"]
                                       :kaocha/test-paths    ["test/unit"]}]
 :kaocha/fail-fast?                  false
 :kaocha/color?                      true
 :kaocha/reporter                    []
 :kaocha/plugins                     [:kaocha.plugin/randomize
 :kaocha.plugin.randomize/seed       950716166
 :kaocha.plugin.randomize/randomize? true
 :kaocha.plugin.profiling/count      3
 :kaocha.plugin.profiling/profiling? true}

Writing a full test configuration by hand is tedious, which is why in tests.edn you can use the #kaocha/v1 {} tagged reader literal. It allows using plain instead of namespaced keywords, and provides many default values, including:

  • source files are in the src/ folder,
  • test files are in the test/ folder,
  • all test namespaces names end with -test (e.g. my-project.core-test). Also, the default test suite id is :unit (just unit on the command line).

If you have a single test suite with clojure.test style tests in the test directory, then you can start out with a tests.edn with nothing but

#kaocha/v1 {}

Try it out! Use bin/kaocha --print-config to see the resulting test configuration.

If your tests don't seem to run (outcome is 0 tests, 0 assertions, 0 failures), you may need to configure one or more test suites with the correct paths.

In general using #kaocha/v1 {} is highly recommended, however if you need fine grained control you can write the output of --print-config to tests.edn and go from there. The rest of the documentation will generally use the short forms used in #kaocha/v1 {}, rather than using fully qualified keywords.

Configuration is read with Aero, meaning you have access to reader literals like #env, #merge, #ref, and #include.

Additionally kaocha supports an extra #meta-merge reader tag, that works similarly to aero's #merge but will merge a whole subtree with the semantics of meta-merge. This is particularly useful for configuring a cascade of includes that selectively augment and override a base configuration. e.g. imagine a base tests.edn file with a #meta-merge and an #include:

#meta-merge [{:tests [{:id         :unit
              :test-paths ["test/unit"]}
             {:id         :features
             :test-paths ["test/features"]}]
             :kaocha/plugins [:kaocha.plugin.some.required/plugin

        #include "tests.user.edn"]

This setup would allow developers to maintain their own private tests.user.edn file and augment the above configuration with for example their own set of plugins such as the notifier etc.

The primary advantage to using the #meta-merge tag over aero's #merge is that meta-merge will do a deep merge of the tree; meaning developers can more easily inherit changes to the base configuration.

Meta-merge is also applied by default for most keys, with some exceptions listed below. You can use ^:prepend, :^append, and^:replace to control the merging. For example, if you wanted to overide the list of default plugins rather than add on to it, write:

#kaocha/v1 {:plugins ^:replace [:kaocha.plugin/capture-output :kaocha.plugin/orchestra]}

The keys :kaocha/reporter, :kaocha/tests, :kaocha/test-paths, :kaocha/source-paths, :kaocha/ns-patterns are replaced by default. If you prefer to add on to the default namespace paths, write:

#kaocha/v1 {:ns-patterns ^:append ["^test-"]}

Test suites

Test suites are a first class concept in Kaocha. This encourages testing at different levels of abstraction, testing different parts or aspects of the project, or writing different types of tests.

A common division is splitting tests into "unit" and "integration" or "acceptance" tests, but these terms don't have strict definitions. It all depends on what makes sense for your project.

It can also make sense to have test suites for specific parts of an app, or suites that test a certain interface. You could have a "frontend", "backend", and "HTTP API" suite.

In Kaocha a test suite has a :type and an :id. Depending on the type it will also have other attributes like the directories to look for tests, or how to discern test from regular namespaces.

Here's an example of a tests.edn defining two test suites: one named :unit, which has its test files under "test/unit", and one named :features, with its tests under "test/features".

{:tests [{:id         :unit
          :test-paths ["test/unit"]}
         {:id         :features
          :test-paths ["test/features"]}]}

You can now run only the unit tests with bin/kaocha unit, or all tests with bin/kaocha.

Because it's using the #kaocha/v1 {} shorthand these test suites inherit the defaults, this means they are of type :kaocha.type/clojure.test, that they consider files under "src" to be the code under test, and that only namespaces ending in -test are considered test namespaces.

This is what the :unit suite looks like after expansion:

{:kaocha.testable/type :kaocha.type/clojure.test,
 :kaocha.testable/id   :unit,
 :kaocha/ns-patterns   ["-test$"],
 :kaocha/source-paths  ["src"],
 :kaocha/test-paths    ["test/unit"]}

If you don't define any test suites then Kaocha assumes a single :unit test suite.

Disabling Automatic Classpath Handling

Kaocha will add any entries in :kaocha/test-paths to the classpath, if they aren't on there already. This is done so this information doesn't need to be duplicated between tests.edn and your project configuration (deps.edn, project.clj, etc).

However, often people will have these paths in their deps.edn anyway (e.g. in a :test or :dev profile), so they are accessible for interactive evaluation (REPL, in-buffer eval). In some cases you also do not want Kaocha to add these, because it can confuse third-party tools. This is because Kaocha needs a DynamicClassLoader to be able to add classpath entries at runtime. If the current classloader is not a DynamicClassLoader then we set one up ourselves, but there have been cases where this caused issues with other tools.

In these cases you can add :kaocha.testable/skip-add-classpath? false to the test suite definition to disable this behavior.


The main test suite type implemented at the moment is one for clojure.test, the testing library included with Clojure itself.

It takes the following configuration options.

  • :ns-patterns: vector of patterns. Patterns are not regexes, they are strings that get intepreted as regular expressions (do not prepend with #). If one of them matches the namespace name then this namespace is considered a test namespace, and will get loaded as part of Kaocha's "load" step. Defaults to ["-test$"]
  • :source-paths: vector of paths containing source code under test. This is used to determine which files to watch for changes, and can be used by plugins e.g. when doing code coverage analyis. Defaults to ["src"]
  • :test-paths: vector of paths containing tests. These paths are added to the JVM classpath prior to executing this suite, and they are searched for namespaces to load. Defaults to ["test"]


Kaocha can be customized and extended with plugins. Some of these are included with Kaocha, others can be provided by third parties. They are regular Clojure libraries that follow specific conventions.

A plugin has a name, a fully qualified keyword, and can be configured easily, either in tests.edn:

{:plugins [:kaocha.plugin/profiling]}

or from the command line

bin/kaocha --plugin kaocha.plugin/profiling

For plugins in the kaocha.plugin namespace, the namespace can be ommitted from the command line:

bin/kaocha --plugin profiling

Some plugins are needed for the normal functioning of Kaocha. These are added automatically when using the #kaocha/v1 {} reader literal. They are

  • :kaocha.plugin/randomize: randomize test order
  • :kaocha.plugin/filter: allow filtering and "focusing" of tests
  • :kaocha.plugin/capture-output: implements output capturing during tests

Individual plugins can introduce their own configuration options, which can be specified either in tests.edn or on the command line. After enabling a plugin try bin/kaocha --test-help to see which command line flags were added, and use --print-config to see available configuration keys with their default values.


The output that Kaocha generates is dictated by "reporters". Reporters are a concept from clojure.test, but are used in Kaocha regardless of the test type being run.

A reporter is configured with --reporter from the command line, or as :reporter in tests.edn. These reporters are Currently provided:

CLI: --reporter Config: {:kaocha/reporter []}

Print the output as a sequence of dots and other symbols.

  • [ / ] Start/end suite
  • ( / ) Start/end namespace
  • . Pass
  • F Fail
  • E Error

Failures with complete output and error information, as well as a general summary are printed at the end (or when Ctrl-C is pressed). This is a great reporter for when you want it concise but still information-rich.

This is a great all-around reporter. It's concise, but still rich in information.

19 test vars, 55 assertions, 2 errors, 1 failures.

CLI: --reporter Config: {:kaocha/reporter []}

Provides detailed output of test namespaces, vars, and testing blocks. If you make good use of clojure.test's facilities this can be very informative. A good choice for use on CI.

--- :unit ---------------------------
    a passing test var
    a failing test var
    an erroring test var
    multiple assertions
    early exit FAIL
      early exit - exception ERROR

CLI: --reporter Config: {:kaocha/reporter []}

Prints a separate progress bar for each test suite, with progress percentage, and the completed/total number of test vars.

Turns red when a test has failed.

integration:   100% [==================================================] 1/1
       unit:   100% [==================================================] 18/18

19 test vars, 55 assertions, 0 failures.

Reporter that outputs TAP (Test Anything Protocol). Useful for integrating with other tools. See also kaocha-junit-xml.

Prints the clojure.test style events map directly, with some keys like :kaocha/testable filtered out to prevent it from getting too noisy.


Sometimes a single fixed configuration is not enough. If you run tests in different contexts, for instance locally vs on a build server, or you need to support more than one workflow, then it can be useful to be able to vary the configuration.

For these cases Aero has the concept of profiles. Here's a typical example. When used locally you want to use a colorful progress bar, but on CI you want plain text output.

{:reporter #profile {:default
 :color? #profile {:default true :ci false}}

This will work out of the box, since Kaocha will pick up on the CI environment variable that is set by all major CI providers, but you can also specify the profile explicitly.

bin/kaocha --profile :ci

Note that profile combines quite nicely with other Aero reader tags like #merge and #include.

 #profile {:ci {:reporter
                :color? false}}]
{:ci #include ""
 :default #include "tests.defaults.edn"}


You should be able to start with a simple #kaocha/v1 {}, and leave most configuration at its default. This is merely an example of what's possible

{:tests [{;; Every suite must have an :id
          :id :unit

          ;; Directories containing files under test. This is used to
          ;; watch for changes, and when doing code coverage analysis
          ;; through Cloverage. These directories are *not* automatically
          ;; added to the classpath.
          :source-paths ["src"]

          ;; Directories containing tests. These will automatically be
          ;; added to the classpath when running this suite.
          :test-paths ["test"]

          ;; Regex strings to determine whether a namespace contains
          ;; tests. (use strings, not actual regexes, due to a limitation of Aero)
          :ns-patterns ["-test$"]}]

 :plugins [:kaocha.plugin/print-invocations

 ;; Colorize output (use ANSI escape sequences).
 :color?      true

 ;; Watch the file system for changes and re-run. You can change this here to be
 ;; on by default, then disable it when necessary with `--no-watch`.
 :watch?      false

 ;; Specifiy the reporter function that generates output. Must be a namespaced
 ;; symbol, or a vector of symbols. The symbols must refer to vars, which Kaocha
 ;; will make sure are loaded. When providing a vector of symbols, or pointing
 ;; at a var containing a vector, then kaocha will call all referenced functions
 ;; for reporting.

 ;; Enable/disable output capturing.
 :capture-output? true

 ;; Plugin specific configuration. Show the 10 slowest tests of each type, rather
 ;; than only 3.
 :kaocha.plugin.profiling/count 10}

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